WEATHER · CLIMATE NORMALS · 1991–2020
Cheyenne Climate — Averages by Month
What the weather in Cheyenne, 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 | -1.3 °C | 15.8 mm |
| February | -1.0 °C | 21.4 mm |
| March | 3.1 °C | 39.3 mm |
| April | 6.4 °C | 64.8 mm |
| May | 11.6 °C | 82.3 mm · wettest |
| June | 17.5 °C | 57.4 mm |
| July | 21.4 °C · warmest | 43.2 mm |
| August | 20.3 °C | 39.9 mm |
| September | 15.6 °C | 39.1 mm |
| October | 8.3 °C | 41.6 mm |
| November | 2.4 °C | 24.3 mm |
| December | -1.5 °C · coldest | 19.8 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 Cheyenne — centred at 41.25°N, 104.75°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.