Lonta Research · HVAC seasonality calendar
Compare the heating and cooling calendar in 24 US cities. We analyzed NOAA's monthly climate normals and kept each airport station, measurement period and quality flag attached to the numbers.
city reference stations
12 months · 65°F base
1991–2020 climate normals
Analysis by Lonta AI · NOAA source files checked October 9, 2026 · Version 1.0
Choose airport stations near your markets. Both charts use the same scale and start at zero. These are historical climate normals, not this year's weather or a forecast of leads.
Cooling degree days · 65°F base · 1991–2020 normals · Dallas–Fort Worth and Phoenix
First market
DALLAS FT WORTH AP, TX US
NOAA station USW00003927
Comparison market
PHOENIX SKY HARBOR INTL AP, AZ US
NOAA station USW00023183
* NOAA flag X: a nonzero value rounded to zero. The three-month share describes weather concentration, not a share of annual calls, jobs or advertising spend. Station-year coverage and completeness flags are in the records below.
The highest cooling normal is 643.0 °F-days in August at Dallas–Fort Worth Airport, and 945.4 °F-days in July at Phoenix Sky Harbor. A single “July is the peak” calendar loses that distinction.
Inspect Dallas's source values ↓The three largest cooling months contain 83.3% of Boston Logan's 12-month cooling total and 37.0% at Miami International. This is weather concentration. It does not say what fraction of each contractor's jobs happens then.
Inspect Miami's source values ↓Coastal stations add another complication: San Francisco International's largest cooling normal occurs in September. Los Angeles International peaks in August. An airport can also be cooler than an inland service area, so match the reference point to the addresses your crews actually reach.
Use a local calendar to choose what to check: staffed phone hours, technician availability, maintenance outreach and landing-page promises. Your own completed jobs, equipment mix and service-area conditions determine the business plan.
Peak means the largest published monthly normal at this station. The three-month share uses the three largest cooling months, which need not be June–August. This selection is not a ranking or a representative sample of all US markets.
| City reference | Heating peak | Cooling peak | Cooling in three largest months |
|---|---|---|---|
| Atlanta, GA ↓ | January | July | 65.9% |
| Austin, TX ↓ | January | August | 58.0% |
| Boston, MA ↓ | January | July | 83.3% |
| Charlotte, NC ↓ | January | July | 70.1% |
| Chicago, IL ↓ | January | July | 79.9% |
| Dallas–Fort Worth, TX ↓ | January | August | 63.4% |
| Denver, CO ↓ | December | July | 84.4% |
| Detroit, MI ↓ | January | July | 81.7% |
| Houston, TX ↓ | January | August | 54.4% |
| Las Vegas, NV ↓ | December | July | 64.0% |
| Los Angeles, CA ↓ | December | August | 66.2% |
| Miami, FL ↓ | January | August | 37.0% |
| Minneapolis, MN ↓ | January | July | 83.0% |
| Nashville, TN ↓ | January | July | 69.7% |
| New York, NY ↓ | January | July | 82.0% |
| Orlando, FL ↓ | January | August | 45.7% |
| Phoenix, AZ ↓ | December | July | 55.6% |
| Portland, OR ↓ | December | August | 83.7% |
| Raleigh, NC ↓ | January | July | 70.0% |
| San Antonio, TX ↓ | January | August | 56.4% |
| San Diego, CA ↓ | December | August | 68.1% |
| San Francisco, CA ↓ | January | September | 64.9% |
| Seattle, WA ↓ | December | August | 84.8% |
| Tampa, FL ↓ | January | August | 43.5% |
Open a station record below for all twelve months and the underlying completeness/year flags. A monthly total also reflects month length; it is not a daily intensity measure.
S = Standard; R = Representative. The number beside the flag is NOAA's years field for that variable and month. X marks a nonzero value rounded to zero. The downloads retain these fields separately.
ATLANTA HARTSFIELD INTL AP, GA US
Latitude 33.63 · Longitude -84.4417 · Elevation 307.8 m
Lowest combined heating + cooling normal: April. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 626.7 | 0.6 | S25 / S25 |
| February | 462.5 | 2.0 | S25 / S25 |
| March | 308.5 | 17.1 | S25 / S25 |
| April | 119.7 | 64.2 | S24 / S24 |
| May | 21.9 | 214.0 | S25 / S25 |
| June | 1.1 | 386.5 | S25 / S25 |
| July | 0.0 | 494.4 | S25 / S25 |
| August | 0.1 | 469.7 | S24 / S24 |
| September | 5.4 | 302.3 | S25 / S25 |
| October | 98.6 | 87.8 | S26 / S26 |
| November | 335.9 | 10.4 | S25 / S25 |
| December | 550.5 | 1.9 | S25 / S25 |
AUSTIN BERGSTROM AP, TX US
Latitude 30.1831 · Longitude -97.68 · Elevation 146.3 m
Lowest combined heating + cooling normal: April. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 469.5 | 7.7 | R24 / R24 |
| February | 321.0 | 20.0 | R24 / R24 |
| March | 183.7 | 61.3 | R24 / R24 |
| April | 52.1 | 145.1 | R24 / R24 |
| May | 3.8 | 344.8 | R24 / R24 |
| June | 0.0 | 517.4 | R24 / R24 |
| July | 0.0 | 606.0 | R24 / R24 |
| August | 0.0 | 613.7 | R24 / R24 |
| September | 1.2 | 422.7 | S25 / S25 |
| October | 44.4 | 194.8 | R24 / R24 |
| November | 219.3 | 48.4 | S26 / S26 |
| December | 423.2 | 14.1 | R25 / R25 |
BOSTON LOGAN INTL AP, MA US
Latitude 42.3606 · Longitude -71.0106 · Elevation 3.7 m
Lowest combined heating + cooling normal: September. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 1,086.4 | 0.0 | S28 / S28 |
| February | 929.6 | 0.0 | S28 / S28 |
| March | 828.2 | 0.5 | S28 / S28 |
| April | 496.1 | 4.1 | S28 / S28 |
| May | 233.9 | 29.3 | S28 / S28 |
| June | 49.8 | 138.2 | S27 / S27 |
| July | 4.0 | 284.4 | S27 / S27 |
| August | 4.8 | 245.0 | S27 / S27 |
| September | 71.3 | 90.7 | S27 / S27 |
| October | 325.5 | 9.3 | S27 / S27 |
| November | 607.8 | 0.3 | S27 / S27 |
| December | 908.3 | 0.0 | S27 / S27 |
CHARLOTTE DOUGLAS AP, NC US
Latitude 35.2236 · Longitude -80.9553 · Elevation 221.9 m
Lowest combined heating + cooling normal: May. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 711.6 | 0.2 | S28 / S28 |
| February | 540.5 | 1.5 | S27 / S27 |
| March | 391.5 | 10.2 | S28 / S28 |
| April | 162.6 | 47.1 | S28 / S28 |
| May | 39.3 | 164.8 | S28 / S28 |
| June | 1.9 | 348.3 | S28 / S28 |
| July | 0.1 | 468.1 | S29 / S29 |
| August | 0.1 | 423.2 | S29 / S29 |
| September | 13.1 | 244.1 | S29 / S29 |
| October | 151.5 | 53.9 | S29 / S29 |
| November | 415.1 | 5.7 | S29 / S29 |
| December | 630.6 | 1.4 | S28 / S28 |
CHICAGO OHARE INTL AP, IL US
Latitude 41.995 · Longitude -87.9336 · Elevation 200.6 m
Lowest combined heating + cooling normal: September. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 1,233.5 | 0.0 | S28 / S28 |
| February | 1,014.9 | 0.0* | S29 / S29 |
| March | 808.1 | 2.0 | S28 / S28 |
| April | 468.2 | 7.7 | S28 / S28 |
| May | 198.0 | 60.0 | S28 / S28 |
| June | 31.4 | 199.3 | S28 / S28 |
| July | 1.8 | 325.6 | S28 / S28 |
| August | 4.1 | 276.8 | S28 / S28 |
| September | 77.2 | 116.1 | S28 / S28 |
| October | 354.8 | 15.4 | S28 / S28 |
| November | 712.9 | 0.4 | S27 / S27 |
| December | 1,069.3 | 0.0 | S28 / S28 |
DALLAS FT WORTH AP, TX US
Latitude 32.8978 · Longitude -97.0189 · Elevation 170.7 m
Lowest combined heating + cooling normal: April. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 582.0 | 2.4 | S25 / S25 |
| February | 413.4 | 7.5 | S26 / S26 |
| March | 246.2 | 35.4 | S25 / S25 |
| April | 82.4 | 101.9 | S26 / S26 |
| May | 9.9 | 290.4 | S26 / S26 |
| June | 0.1 | 505.5 | S25 / S25 |
| July | 0.0 | 641.6 | S25 / S25 |
| August | 0.0 | 643.0 | S25 / S25 |
| September | 3.4 | 409.8 | S24 / S24 |
| October | 69.2 | 154.5 | S24 / S24 |
| November | 285.2 | 27.3 | S24 / S24 |
| December | 528.3 | 4.5 | S25 / S25 |
DENVER INTL AP, CO US
Latitude 39.8328 · Longitude -104.6575 · Elevation 1,650.2 m
Lowest combined heating + cooling normal: June. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 1,033.9 | 0.0 | S25 / S25 |
| February | 904.2 | 0.0 | S25 / S25 |
| March | 725.6 | 0.0* | S26 / S26 |
| April | 517.1 | 1.2 | S25 / S25 |
| May | 261.3 | 25.7 | S25 / S25 |
| June | 51.5 | 147.4 | S25 / S25 |
| July | 3.8 | 315.2 | R22 / R22 |
| August | 9.3 | 254.1 | S25 / S25 |
| September | 105.3 | 99.2 | S25 / S25 |
| October | 435.8 | 6.6 | S25 / S25 |
| November | 766.6 | 0.1 | S25 / S25 |
| December | 1,047.6 | 0.0 | S25 / S25 |
DETROIT METRO AP, MI US
Latitude 42.2314 · Longitude -83.3308 · Elevation 192.3 m
Lowest combined heating + cooling normal: September. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 1,216.5 | 0.0 | S25 / S25 |
| February | 1,035.9 | 0.0* | S25 / S25 |
| March | 860.9 | 0.7 | S25 / S25 |
| April | 487.5 | 4.5 | S25 / S25 |
| May | 197.7 | 50.4 | S27 / S27 |
| June | 28.1 | 176.5 | S27 / S27 |
| July | 2.4 | 282.8 | S26 / S26 |
| August | 6.6 | 232.8 | S26 / S26 |
| September | 91.4 | 89.7 | S26 / S26 |
| October | 381.6 | 9.6 | S26 / S26 |
| November | 712.5 | 0.0* | S26 / S26 |
| December | 1,046.1 | 0.0 | S26 / S26 |
HOUSTON INTERCONT AP, TX US
Latitude 29.98 · Longitude -95.36 · Elevation 29.0 m
Lowest combined heating + cooling normal: March. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 365.9 | 17.2 | S25 / S25 |
| February | 236.0 | 31.7 | S26 / S26 |
| March | 122.5 | 85.3 | S25 / S25 |
| April | 30.9 | 179.4 | S24 / S24 |
| May | 1.2 | 384.0 | S25 / S25 |
| June | 0.0 | 539.9 | S25 / S25 |
| July | 0.0 | 623.1 | S25 / S25 |
| August | 0.0 | 624.6 | S25 / S25 |
| September | 0.3 | 465.3 | S25 / S25 |
| October | 26.5 | 238.8 | S26 / S26 |
| November | 158.2 | 69.7 | S26 / S26 |
| December | 324.8 | 28.8 | S26 / S26 |
LAS VEGAS MCCARRAN AP, NV US
Latitude 36.0719 · Longitude -115.1633 · Elevation 649.5 m
Lowest combined heating + cooling normal: April. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 480.5 | 0.0* | S27 / S27 |
| February | 323.3 | 1.3 | S27 / S27 |
| March | 166.2 | 36.0 | S28 / S28 |
| April | 54.8 | 135.8 | S27 / S27 |
| May | 8.2 | 389.5 | S28 / S28 |
| June | 0.7 | 678.6 | S28 / S28 |
| July | 0.0 | 875.6 | S28 / S28 |
| August | 0.0 | 827.6 | S28 / S28 |
| September | 0.3 | 559.7 | S27 / S27 |
| October | 32.5 | 199.9 | S27 / S27 |
| November | 250.0 | 16.0 | S27 / S27 |
| December | 519.1 | 0.1 | S27 / S27 |
LOS ANGELES INTL AP, CA US
Latitude 33.9381 · Longitude -118.3889 · Elevation 29.6 m
Lowest combined heating + cooling normal: June. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 227.4 | 5.8 | S27 / S27 |
| February | 207.3 | 7.1 | S27 / S27 |
| March | 189.8 | 8.5 | S26 / S26 |
| April | 132.5 | 17.0 | S26 / S26 |
| May | 69.5 | 24.5 | S26 / S26 |
| June | 13.0 | 56.5 | S26 / S26 |
| July | 1.5 | 142.5 | S26 / S26 |
| August | 1.0 | 179.2 | S26 / S26 |
| September | 2.4 | 155.4 | S27 / S27 |
| October | 26.0 | 91.1 | S26 / S26 |
| November | 111.2 | 30.2 | S26 / S26 |
| December | 232.0 | 2.6 | S26 / S26 |
MIAMI INTL AP, FL US
Latitude 25.7906 · Longitude -80.3164 · Elevation 8.8 m
Lowest combined heating + cooling normal: January. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 43.7 | 155.5 | R25 / R25 |
| February | 22.0 | 181.5 | S26 / S26 |
| March | 8.4 | 259.5 | S26 / S26 |
| April | 0.5 | 351.5 | S26 / S26 |
| May | 0.0* | 466.5 | S26 / S26 |
| June | 0.0 | 534.0 | S26 / S26 |
| July | 0.0 | 590.5 | S27 / S27 |
| August | 0.0 | 595.2 | S27 / S27 |
| September | 0.0 | 538.5 | S27 / S27 |
| October | 0.2 | 466.7 | S27 / S27 |
| November | 3.3 | 297.3 | S27 / S27 |
| December | 25.5 | 219.3 | S26 / S26 |
MINNEAPOLIS/ST PAUL AP, MN US
Latitude 44.8831 · Longitude -93.2289 · Elevation 265.8 m
Lowest combined heating + cooling normal: June. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 1,512.6 | 0.0 | S27 / S27 |
| February | 1,243.1 | 0.0 | S27 / S27 |
| March | 983.2 | 0.4 | S27 / S27 |
| April | 542.2 | 3.7 | S27 / S27 |
| May | 213.9 | 44.9 | S27 / S27 |
| June | 34.4 | 175.3 | S26 / S26 |
| July | 4.3 | 294.0 | S26 / S26 |
| August | 10.3 | 219.5 | S26 / S26 |
| September | 127.6 | 84.0 | S27 / S27 |
| October | 488.6 | 8.1 | S27 / S27 |
| November | 906.0 | 0.1 | S27 / S27 |
| December | 1,332.9 | 0.0 | S27 / S27 |
NASHVILLE INTL AP, TN US
Latitude 36.1189 · Longitude -86.6892 · Elevation 182.9 m
Lowest combined heating + cooling normal: May. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 787.5 | 0.3 | S27 / S27 |
| February | 606.1 | 1.3 | S27 / S27 |
| March | 430.7 | 10.6 | S27 / S27 |
| April | 179.7 | 52.2 | S26 / S26 |
| May | 41.9 | 176.7 | S26 / S26 |
| June | 1.3 | 362.8 | S26 / S26 |
| July | 0.0* | 486.7 | S26 / S26 |
| August | 0.1 | 455.8 | S26 / S26 |
| September | 14.4 | 257.3 | S25 / S25 |
| October | 164.6 | 62.2 | S26 / S26 |
| November | 446.9 | 6.0 | S27 / S27 |
| December | 690.8 | 1.1 | S26 / S26 |
NEW YORK JFK INTL AP, NY US
Latitude 40.6386 · Longitude -73.7622 · Elevation 3.4 m
Lowest combined heating + cooling normal: September. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 996.5 | 0.0 | S27 / S27 |
| February | 852.6 | 0.0 | S27 / S27 |
| March | 739.3 | 0.0* | S27 / S27 |
| April | 426.8 | 2.4 | S27 / S27 |
| May | 171.2 | 30.2 | S28 / S28 |
| June | 20.8 | 176.7 | S28 / S28 |
| July | 0.3 | 345.8 | S27 / S27 |
| August | 0.8 | 310.7 | S27 / S27 |
| September | 33.4 | 135.3 | S27 / S27 |
| October | 255.4 | 15.2 | S27 / S27 |
| November | 546.1 | 0.1 | S27 / S27 |
| December | 829.2 | 0.0 | S27 / S27 |
ORLANDO INTL AP, FL US
Latitude 28.4339 · Longitude -81.325 · Elevation 27.4 m
Lowest combined heating + cooling normal: February. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 180.1 | 45.5 | S26 / S26 |
| February | 104.8 | 66.9 | S27 / S27 |
| March | 54.4 | 127.3 | S27 / S27 |
| April | 9.6 | 224.1 | S27 / S27 |
| May | 0.5 | 383.3 | S27 / S27 |
| June | 0.0 | 485.9 | S27 / S27 |
| July | 0.0 | 545.6 | S27 / S27 |
| August | 0.0 | 547.1 | S26 / S26 |
| September | 0.0* | 479.9 | S26 / S26 |
| October | 5.5 | 329.4 | S26 / S26 |
| November | 42.6 | 140.2 | S26 / S26 |
| December | 127.4 | 76.3 | S26 / S26 |
PHOENIX SKY HARBOR INTL AP, AZ US
Latitude 33.4278 · Longitude -112.0039 · Elevation 337.4 m
Lowest combined heating + cooling normal: March. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 256.2 | 2.0 | S28 / S28 |
| February | 159.0 | 16.3 | S27 / S27 |
| March | 64.7 | 105.0 | S27 / S27 |
| April | 14.3 | 258.9 | S27 / S27 |
| May | 0.8 | 527.8 | S27 / S27 |
| June | 0.0 | 791.9 | S27 / S27 |
| July | 0.0 | 945.4 | S27 / S27 |
| August | 0.0 | 909.8 | S27 / S27 |
| September | 0.0 | 727.4 | S27 / S27 |
| October | 5.8 | 390.2 | S27 / S27 |
| November | 85.0 | 88.1 | S27 / S27 |
| December | 288.5 | 1.9 | S28 / S28 |
PORTLAND INTL AP, OR US
Latitude 45.5908 · Longitude -122.6003 · Elevation 5.8 m
Lowest combined heating + cooling normal: September. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 717.7 | 0.0 | S27 / S27 |
| February | 583.8 | 0.0 | S27 / S27 |
| March | 519.3 | 0.0* | S27 / S27 |
| April | 366.6 | 2.1 | S27 / S27 |
| May | 196.0 | 20.9 | S27 / S27 |
| June | 80.0 | 56.0 | S29 / S29 |
| July | 10.2 | 171.3 | S29 / S29 |
| August | 7.4 | 181.0 | S29 / S29 |
| September | 60.9 | 72.8 | S29 / S29 |
| October | 296.5 | 3.6 | S29 / S29 |
| November | 538.5 | 0.0 | S28 / S28 |
| December | 726.9 | 0.0 | S27 / S27 |
RALEIGH DURHAM INTL AP, NC US
Latitude 35.8922 · Longitude -78.7819 · Elevation 126.8 m
Lowest combined heating + cooling normal: May. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 718.0 | 0.5 | S29 / S29 |
| February | 561.7 | 1.7 | S29 / S29 |
| March | 420.9 | 11.8 | S29 / S29 |
| April | 180.0 | 54.0 | S29 / S29 |
| May | 46.8 | 166.1 | S29 / S29 |
| June | 3.1 | 354.1 | S29 / S29 |
| July | 0.0* | 480.4 | S29 / S29 |
| August | 0.1 | 427.8 | S29 / S29 |
| September | 14.7 | 242.6 | S29 / S29 |
| October | 159.8 | 56.0 | S29 / S29 |
| November | 411.9 | 7.0 | S29 / S29 |
| December | 636.3 | 2.5 | S29 / S29 |
SAN ANTONIO INTL AP, TX US
Latitude 29.5442 · Longitude -98.4839 · Elevation 240.5 m
Lowest combined heating + cooling normal: April. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 405.5 | 7.3 | S26 / S26 |
| February | 265.9 | 22.3 | S26 / S26 |
| March | 139.2 | 71.0 | S26 / S26 |
| April | 35.2 | 165.7 | S25 / S25 |
| May | 2.8 | 359.3 | S25 / S25 |
| June | 0.0 | 526.4 | S25 / S25 |
| July | 0.0 | 613.8 | R23 / R23 |
| August | 0.0 | 633.8 | S24 / S24 |
| September | 1.0 | 446.5 | S24 / S24 |
| October | 34.0 | 229.3 | S24 / S24 |
| November | 185.6 | 58.1 | S25 / S25 |
| December | 369.2 | 14.3 | S26 / S26 |
SAN DIEGO LINDBERGH FLD, CA US
Latitude 32.7336 · Longitude -117.1831 · Elevation 4.6 m
Lowest combined heating + cooling normal: May. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 209.2 | 3.0 | R23 / R23 |
| February | 172.8 | 4.8 | R23 / R23 |
| March | 141.5 | 9.8 | R23 / R23 |
| April | 84.7 | 23.2 | R23 / R23 |
| May | 44.8 | 37.0 | R22 / R22 |
| June | 10.2 | 74.7 | R22 / R22 |
| July | 0.6 | 177.3 | R23 / R23 |
| August | 0.1 | 229.5 | R23 / R23 |
| September | 0.4 | 201.3 | R23 / R23 |
| October | 11.4 | 105.9 | S24 / S24 |
| November | 93.0 | 25.5 | R23 / R23 |
| December | 221.2 | 1.2 | R23 / R23 |
SAN FRANCISCO INTL AP, CA US
Latitude 37.6197 · Longitude -122.3647 · Elevation 2.4 m
Lowest combined heating + cooling normal: July. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 426.2 | 0.0 | S26 / S26 |
| February | 323.4 | 0.0* | S26 / S26 |
| March | 295.5 | 1.0 | S26 / S26 |
| April | 234.3 | 4.8 | R25 / R25 |
| May | 170.0 | 13.5 | S26 / S26 |
| June | 96.9 | 23.4 | S26 / S26 |
| July | 58.4 | 25.9 | S25 / S25 |
| August | 44.0 | 40.9 | S26 / S26 |
| September | 45.8 | 56.3 | S26 / S26 |
| October | 99.5 | 32.8 | S26 / S26 |
| November | 259.6 | 1.7 | S26 / S26 |
| December | 421.5 | 0.0 | S26 / S26 |
SEATTLE TACOMA INTL AP, WA US
Latitude 47.4444 · Longitude -122.3139 · Elevation 112.8 m
Lowest combined heating + cooling normal: August. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 686.7 | 0.0 | S27 / S27 |
| February | 588.0 | 0.0 | S27 / S27 |
| March | 556.6 | 0.2 | S26 / S26 |
| April | 411.9 | 0.9 | S26 / S26 |
| May | 241.8 | 9.3 | S26 / S26 |
| June | 117.9 | 29.4 | S26 / S26 |
| July | 31.1 | 96.1 | S25 / S25 |
| August | 23.7 | 98.1 | S25 / S25 |
| September | 102.4 | 30.4 | S26 / S26 |
| October | 349.3 | 0.5 | S27 / S27 |
| November | 555.0 | 0.0 | S27 / S27 |
| December | 711.4 | 0.0 | S27 / S27 |
TAMPA INTL AP, FL US
Latitude 27.9619 · Longitude -82.5403 · Elevation 5.8 m
Lowest combined heating + cooling normal: February. This is an unweighted weather calculation, not a prediction of a slow business month.
| Month | Heating | Cooling | Heating / cooling flags & years |
|---|---|---|---|
| January | 152.1 | 60.9 | S29 / S29 |
| February | 88.1 | 81.1 | S29 / S29 |
| March | 44.2 | 154.3 | S28 / S28 |
| April | 6.7 | 273.7 | S28 / S28 |
| May | 0.3 | 448.2 | S28 / S28 |
| June | 0.0 | 538.4 | S28 / S28 |
| July | 0.0 | 582.8 | S28 / S28 |
| August | 0.0 | 589.0 | S28 / S28 |
| September | 0.0* | 532.4 | S28 / S28 |
| October | 3.4 | 387.8 | S28 / S28 |
| November | 33.7 | 177.8 | S29 / S29 |
| December | 104.8 | 101.7 | S29 / S29 |
We selected 24 US city references to show different regional patterns, using one identifiable airport station for each. This is a purposive selection, not a population-weighted national estimate, a list of the biggest markets or a sample of our clients. Station names and coordinates are NOAA's, including historical airport names in the source files.
On October 9, 2026, we downloaded each station's original monthly file from NOAA NCEI's 1991–2020 U.S. Climate Normals. We extracted MLY-HTDD-NORMAL and MLY-CLDD-NORMAL, their measurement and completeness flags, and their years fields. Both variables use a 65°F base. There are 288 station-month records and 576 degree-day values; months and variables are not independent weather stations.
A degree day accumulates temperature departure from a base. In the National Weather Service's daily explanation, a 78°F daily mean gives 13 cooling degree days above 65°F; a 29°F mean gives 36 heating degree days below it. A monthly total combines days. It does not count days with broken air conditioners or households ready to buy.
We use NOAA's published monthly degree-day variables directly. We do not estimate them by subtracting 65°F from a monthly mean temperature. NOAA's constrained daily temperatures and normals methodology supply the original calculations.
All 576 selected values are present. NOAA marks 526 Standard and 50 Representative; 13 have an X measurement flag for rounding to zero. These flags are copied from the source, not reclassified from their year counts. NOAA can estimate missing years using surrounding stations. A 30-year normal therefore does not mean every value has 30 complete observed years.
The period is 1991–2020. It describes a historical baseline, not current weather, recent warming or an upcoming heat wave. Airport siting, coastlines, elevation and urban conditions can make your service area differ. Humidity, equipment stock, household income, outages, maintenance plans, auction competition and your capacity are outside this dataset.
No jobs, leads, search volumes, ad-account records or revenue observations are included. The calculations do not estimate contractor demand or advertising lift. The checks establish that the selected records and calculations match the published NOAA files; they are not an independent audit of NOAA's underlying climate model.
Free, without registration. The 288-row CSV and JSON keep coordinates, period, units, flags, year counts, original station URLs and source-file hashes. The chart summarizes the peak months; the complete records remain the reference.
Suggested citation
Lonta AI. HVAC Seasonality Calendar: 24 US City Reference Stations. Version 1.0. Analysis of NOAA NCEI's 1991–2020 monthly climate normals. Source files retrieved October 9, 2026. lonta.io/research/hvac-seasonality/.
Cite NOAA for the published climate values and Lonta for the selection, comparison and analysis. Preserve the station, base temperature and normals period when reusing a figure.
Checked October 9, 2026. Each station's original CSV is linked in its record.
Heating and cooling exposure has a local calendar. In this selected NOAA dataset, the largest monthly cooling normal occurs in July at Phoenix Sky Harbor, August at Dallas–Fort Worth Airport and September at San Francisco International. Those station normals do not measure the months with the most service calls or jobs.
No. These are NOAA's monthly climate normals for 1991–2020, downloaded October 9, 2026. A normal describes a historical seasonal pattern. It is not a 2026 observation or a forecast.
The percentages describe the concentration of degree days across months. They do not describe shares of annual leads, repairs, replacements or revenue. Set a budget from your own job economics, available capacity and measured demand, with climate as one planning input.
These are identifiable NOAA station records with monthly degree-day normals, source files and quality flags. One airport is an explicit reference point, not a city-wide average. Coastal neighborhoods, elevation and inland service areas can differ from it.
Use the lead cost calculator for that spending ceiling, and the weather and agency results worksheet to review a claimed improvement. The marketing benchmark evidence review explains how other industry figures change with their definitions.
More Lonta research and tools. Lonta runs HVAC marketing; the free written strategy starts with your own service area and measurement gaps.
