St. Louis weather by month
St. Louis runs from about -1°C in January to 25°C in June, with July the wettest month at 175 mm.
warmest month
June
25°C
coolest month
January
-1°C
wettest month
July
175 mm
worst air month
February
16 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | -1°C | 131 mm | 156 h | 9 |
| February | 6°C | 13 mm | 264 h | 16 |
| March | 10°C | 94 mm | 292 h | 7 |
| April | 15°C | 126 mm | 302 h | 6 |
| May | 21°C | 141 mm | 351 h | 7 |
| June | 25°C | 71 mm | 356 h | 9 |
| July | 25°C | 175 mm | 362 h | 10 |
| August | 25°C | 54 mm | 347 h | 10 |
| September | 22°C | 123 mm | 289 h | 9 |
| October | 16°C | 10 mm | 322 h | 7 |
| November | 10°C | 164 mm | 191 h | 7 |
| December | 4°C | 84 mm | 174 h | 9 |
About 3,406 hours of sun a year. Roughly 117 rainy days a year.
These are long-run climate normals, not a forecast. A given year can sit well outside them. PM2.5 is a global model: near the coast it counts sea salt as fine particulate and reads high against ground stations, sometimes by a factor of two. Use the shape of the year, not the absolute number.
where these numbers come from
- · Temperature, rainfall and sunshine: ECMWF ERA5 reanalysis climate normals via Open-Meteo (CC BY 4.0), fetched once and stored.
- · PM2.5: Copernicus CAMS reanalysis, monthly means. Modelled, not station readings; near coasts CAMS counts sea salt as PM2.5 and reads high.
Last reviewed 2026-05-23. Full method, licences and the list of sources we rejected are on the methodology page.