NOAA's Climate Prediction Center says, "Degree day is a quantitative index demonstrated to reflect demand for energy to heat or cool houses and businesses." This page gives the 1991–2020 heating and cooling degree-day normals from NOAA's National Centers for Environmental Information (NCEI). It covers one weather station for each of our markets, plus a second station for Austin. The normals are long-term averages, not totals for a recent year. This page reports NOAA's numbers only and does not estimate energy use or cost.
What heating and cooling degree days measure
NOAA's Climate Prediction Center explains, "A mean daily temperature (average of the daily maximum and minimum temperatures) of 65°F is the base for both heating and cooling degree day computations. Heating degree days are summations of negative differences between the mean daily temperature and the 65°F base; cooling degree days are summations of positive differences from the same base."
NCEI's documentation for the 1991–2020 normals, a file dated April 26, 2021, describes the annual heating figure as "Long-term averages of annual heating degree days with base 65F." It describes the annual cooling figure as "Long-term averages of annual cooling degree days with base 65F."
Annual degree-day normals by market
The table lists each station as NCEI names it, with its station ID, from NCEI's annual normals data.
| Market | NCEI station name | Station ID | Heating degree days, annual normal | Cooling degree days, annual normal |
|---|---|---|---|---|
| Phoenix | PHOENIX SKY HARBOR INTL AP, AZ US | USW00023183 | 874.3 | 4,764.6 |
| Seattle–Tacoma | SEATTLE TACOMA INTL AP, WA US | USW00024233 | 4,375.8 | 265.0 |
| Austin (primary station) | AUSTIN-CAMP MABRY, TX US | USW00013958 | 1,442.4 | 3,289.9 |
| Austin (second station) | AUSTIN BERGSTROM AP, TX US | USW00013904 | 1,718.3 | 2,995.9 |
| Jacksonville | JACKSONVILLE, FL US | USW00013889 | 1,227.6 | 2,803.2 |
| Columbus, Ohio | COLUMBUS PORT COLUMBUS INTL AP, OH US | USW00014821 | 5,233.4 | 1,067.8 |
NOAA NCEI 1991–2020 normals, base 65°F.
Of these stations, Columbus has the most heating degree days and Phoenix Sky Harbor has the most cooling degree days. Seattle–Tacoma has the fewest cooling degree days, 265.0 a year, and Phoenix Sky Harbor has the fewest heating degree days, 874.3 a year. The Phoenix, Austin and Jacksonville stations all have more cooling degree days than heating degree days in the 1991–2020 normals. Seattle–Tacoma and Columbus have more heating degree days than cooling degree days.
Annual heating and cooling degree days, 1991–2020 normals (base 65°F)
- Phoenix Sky Harbor: heating874.3 degree days
- Phoenix Sky Harbor: cooling4,764.6 degree days
- Seattle–Tacoma: heating4,375.8 degree days
- Seattle–Tacoma: cooling265 degree days
- Austin Camp Mabry: heating1,442.4 degree days
- Austin Camp Mabry: cooling3,289.9 degree days
- Austin Bergstrom (second station): heating1,718.3 degree days
- Austin Bergstrom (second station): cooling2,995.9 degree days
- Jacksonville: heating1,227.6 degree days
- Jacksonville: cooling2,803.2 degree days
- Columbus: heating5,233.4 degree days
- Columbus: cooling1,067.8 degree days
Why this page uses Camp Mabry for Austin
NCEI publishes 1991–2020 normals for both Austin Camp Mabry (USW00013958) and Austin Bergstrom (USW00013904). We use Camp Mabry as the primary Austin station because the National Weather Service's Austin Area climate record was kept there as of the site history's last update. A site history from the NWS Austin/San Antonio office, last updated June 13, 2021, lists the current entry in that record as "July 21, 1999 - present: Camp Mabry Army National Guard Base."
Austin Bergstrom appears here as a second station. Its 1991–2020 normals are 1,718.3 heating and 2,995.9 cooling degree days a year, compared with 1,442.4 and 3,289.9 at Camp Mabry. Some of our earlier Austin articles use the Bergstrom normals, including our guides to whether heat pumps work well in Texas and how long an AC lasts in Texas. This page does not explain the difference between the two stations.
January and July degree-day normals
NCEI also publishes monthly normals. The table shows January and July for each primary station.
| Station (ID) | January heating | January cooling | July heating | July cooling |
|---|---|---|---|---|
| Phoenix Sky Harbor (USW00023183) | 256.2 | 2.0 | 0.0 | 945.4 |
| Seattle–Tacoma (USW00024233) | 686.7 | 0.0 | 31.1 | 96.1 |
| Austin Camp Mabry (USW00013958) | 407.8 | 9.6 | 0.0 | 644.8 |
| Jacksonville (USW00013889) | 349.5 | 14.9 | 0.0 | 544.0 |
| Columbus (USW00014821) | 1,098.6 | 0.0 | 0.5 | 322.8 |
NOAA NCEI 1991–2020 monthly normals, base 65°F. This table does not include monthly normals for Austin Bergstrom.
Columbus's January normal of 1,098.6 heating degree days is the highest January figure in the table. Phoenix Sky Harbor's July normal of 945.4 cooling degree days is the highest July figure. Seattle–Tacoma's July normal still includes 31.1 heating degree days, and Columbus's July normal includes 0.5.
What these normals do not show
These figures are 1991–2020 averages, not totals for any single year, and we did not pull recent-year totals. NCEI's readme for the normals files, dated April 24, 2021, says, "Note that NORMAL with degree days is base 65." This page uses only those base-65 normals.
This page does not convert degree days into energy use, bills or equipment sizes. To compare running costs with your own power and gas prices, use our heat pump vs furnace operating cost calculator. For local questions, see our guides on whether you need AC in Seattle and choosing a heat pump or gas furnace in Ohio.