WEATHER · CLIMATE NORMALS · 1991–2020
Washington Climate — Averages by Month
What the weather in Washington, USaverages across a standard 30-year period. Each month's figure is the 1991–2020 mean temperature and total rainfall from the ERA5 reanalysis — the long-run normal a place settles around, not a forecast for any particular day.
Month-by-month normals
| Month | Avg temperature | Avg rainfall |
|---|---|---|
| January | 1.8 °C · coldest | 81.4 mm |
| February | 3.1 °C | 75.7 mm |
| March | 7.3 °C | 101.4 mm |
| April | 13.4 °C | 89.5 mm |
| May | 18.5 °C | 98.3 mm |
| June | 23.5 °C | 93.3 mm |
| July | 26.0 °C · warmest | 106.2 mm |
| August | 24.8 °C | 92.4 mm |
| September | 20.9 °C | 111.2 mm · wettest |
| October | 14.4 °C | 88.6 mm |
| November | 8.6 °C | 76.0 mm |
| December | 4.0 °C | 91.8 mm |
How to read these numbers
These are reanalysis normals, not readings from a single weather station. They come from the ERA5 0.25° (~25 km) global reanalysis grid, sampled at the grid cell nearest Washington — centred at 39.00°N, 77.00°W. A reanalysis blends observations with a physics model onto an even grid, so a coastal or mountain city's cell can read a little cooler, warmer, wetter or drier than the city centre itself. The month-to-month shape — when it's hot, when it rains — is what these normals capture best.
“Normal” means the 1991–2020 average, the current World Meteorological Organization standard period. A normal is what a place tends toward over decades — any single day, month or year can and will depart from it.