WEATHER · CLIMATE NORMALS · 1991–2020
Pierre Climate — Averages by Month
What the weather in Pierre, 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 | -7.0 °C · coldest | 18.8 mm |
| February | -4.8 °C | 24.4 mm |
| March | 1.2 °C | 35.9 mm |
| April | 8.0 °C | 66.5 mm |
| May | 14.9 °C | 86.3 mm |
| June | 20.8 °C | 93.3 mm · wettest |
| July | 24.4 °C · warmest | 67.3 mm |
| August | 23.2 °C | 59.6 mm |
| September | 17.9 °C | 48.0 mm |
| October | 9.5 °C | 50.2 mm |
| November | 1.2 °C | 24.3 mm |
| December | -5.1 °C | 21.2 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 Pierre — centred at 44.25°N, 100.25°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.