Climate averages 1991–2020
St. Louis weather
by month.
See how the year changes. July has the highest average daily maximum; February has the lowest average monthly rainfall.
Pleasant-weather months by our simple rule: September
Long-term climate patterns, not a forecast for a particular trip.
Across the year St. Louis averages a daytime high of 18.6°C and a nighttime low of 9.1°C, with about 1,066 mm of rain on roughly 114 days. July is the warmest month (average high 31.0°C) and January the coolest (4.3°C). May is the wettest month with 128 mm; February is the driest with 63 mm.
Months with pleasant weather by a simple rule (average high between 18°C and 29°C, average low of at least 5°C and at most 8 rain days): September. This looks at temperature and rain only, not humidity, wind, sea temperature or crowds.
The annual picture
A year in St. Louis
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
St. Louis climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 4.3°C-4.3°C | -4.3°C | 70 | 8.2 | 9.810 h |
| February | 7.2°C-2.5°C | -2.5°C | 63 | 7.8 | 10.711 h |
| March | 13.0°C2.6°C | 2.6°C | 94 | 10.5 | 11.912 h |
| April | 19.1°C8.4°C | 8.4°C | 117 | 11.2 | 13.213 h |
| May | 24.3°C14.3°C | 14.3°C | 128 | 13.4 | 14.314 h |
| June | 29.1°C19.3°C | 19.3°C | 106 | 11.0 | 14.815 h |
| July | 31.0°C21.6°C | 21.6°C | 86 | 9.9 | 14.615 h |
| August | 30.4°C20.9°C | 20.9°C | 74 | 9.1 | 13.714 h |
| September | 26.4°C16.6°C | 16.6°C | 83 | 7.6 | 12.512 h |
| October | 19.9°C10.3°C | 10.3°C | 87 | 8.4 | 11.211 h |
| November | 12.3°C3.6°C | 3.6°C | 93 | 8.6 | 10.110 h |
| December | 6.3°C-1.7°C | -1.7°C | 65 | 8.2 | 9.510 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
Nearby cities
- O'FallonUnited States · 48 kmHigh 18.3°C · Low 9.1°C · 1,030 mm rain a year
- Springfield (Illinois), United StatesUnited States · 139 kmHigh 16.8°C · Low 7.6°C · 1,015 mm rain a year
- DecaturUnited States · 172 kmHigh 16.6°C · Low 7.5°C · 1,050 mm rain a year
- Columbia (Missouri), United StatesUnited States · 189 kmHigh 18.2°C · Low 8.8°C · 1,051 mm rain a year
- Bloomington (Illinois), United StatesUnited States · 231 kmHigh 15.8°C · Low 6.7°C · 1,008 mm rain a year
- Peoria (Illinois), United StatesUnited States · 236 kmHigh 15.9°C · Low 7.1°C · 979 mm rain a year
- ChampaignUnited States · 236 kmHigh 16.2°C · Low 7.0°C · 1,027 mm rain a year
- EvansvilleUnited States · 242 kmHigh 19.0°C · Low 10.1°C · 1,173 mm rain a year
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsWhat do the high and low temperatures mean?
We average the daily maximum and daily minimum for each calendar month over 1991–2020. They are not record extremes, a forecast range or temperatures at a fixed time of day.
How is a rain day counted?
A local calendar day (standard time, UTC-6, no daylight saving) with at least 1 mm of total precipitation counts as one rain day. We count these for each year and month, then average across 30 years. The average does not predict which days will be wet.
Where do the numbers come from?
ERA5-Land (temperature) and ERA5 (precipitation) reanalysis from the Copernicus Climate Change Service, read from the Open-Meteo open-data archive. Temperature comes from the 0.1° model cell at 38.60°, -90.20° (3 km from the city centre), adjusted down by 0.1°C for the difference between the city's elevation (149 m) and the cell's (140 m). Rain comes from the 0.25° cell at 38.75°, -90.25°. These are model estimates, not weather-station readings; coast, hills and city streets can differ.
Does this page show sunshine, humidity or sea temperature?
No. The data used here contain air temperature and precipitation only. Daylight hours are calculated from the city's latitude (sunrise to sunset), not measured sunshine.