WEATHER · CLIMATE NORMALS · 1991–2020
St Louis Climate — Averages by Month
What the weather in St Louis, 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 | -0.4 °C · coldest | 73.4 mm |
| February | 2.1 °C | 65.9 mm |
| March | 7.6 °C | 96.6 mm |
| April | 13.8 °C | 119.3 mm |
| May | 19.3 °C | 130.9 mm · wettest |
| June | 24.2 °C | 109.6 mm |
| July | 26.0 °C · warmest | 88.9 mm |
| August | 25.1 °C | 77.5 mm |
| September | 20.8 °C | 85.9 mm |
| October | 14.4 °C | 88.8 mm |
| November | 7.5 °C | 95.4 mm |
| December | 2.0 °C | 68.5 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 St Louis — centred at 38.75°N, 90.25°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.