St Louis records about 1042mm of rain across roughly 107 wet days a year, which is a 29% chance on an average day. May is the wettest month at 108mm (10% of the annual total) and January the driest at 48mm. Local rain type: thunderstorms. St. Louis sits in the Mississippi River corridor — severe thunderstorms and tornadoes are a spring/summer concern. The Gateway Arch is a perfect rainy-day visit.
Chance of rain on an average day: 29%
Rainfall climatology for St Louis. The live hour-by-hour answer for today loads at the top of this page from Open-Meteo and refreshes through the day — the figures below describe a typical year, not today.
Last updated: · Live forecast data refreshes hourly.
| Annual rainfall | 1042mm |
| Rain days per year | 107 |
| Odds on an average day | 29% |
| Wettest month | May — 108mm over 12 days |
| Driest month | January — 48mm over 5 days |
| Rain type | thunderstorms |
| Best dry window | September and October offer dry, comfortable conditions. |
| Worst rain window | April through June brings severe thunderstorm season. |
May delivers 125% more rain than January (108mm vs 48mm). That gap is the difference between planning around showers and ignoring them.
No single month holds more than 10% of the annual total, so rain in St Louis is spread through the year — there is no season you can rely on being dry.
St Louis rain arrives in short, heavy bursts — shelter and timing matter more than gear.
Rain falls on about 12 days in May against 5 in January — the frequency swing matters more for planning than the millimetre totals.
Climate normals. Use them to judge whether today's live forecast at the top of the page is typical or unusual for the season.
| Month | Rainfall | Rain days | Chance on a given day | Highs |
|---|---|---|---|---|
| January | 48mm | 5 | 17% | 4°C |
| February | 52mm | 6 | 20% | 4°C |
| March | 72mm | 8 | 27% | 8°C |
| April | 98mm | 11 | 37% | 14°C |
| May | 108mm | 12 | 40% | 22°C |
| June | 105mm | 12 | 40% | 28°C |
| July | 98mm | 11 | 37% | 32°C |
| August | 72mm | 8 | 27% | 32°C |
| September | 78mm | 9 | 30% | 28°C |
| October | 78mm | 9 | 30% | 22°C |
| November | 85mm | 9 | 30% | 14°C |
| December | 72mm | 8 | 27% | 8°C |
Rain probability is the chance that at least 0.2mm falls at your location — not how long it rains. For St Louis we combine the hourly probability curve, expected volume in millimetres, and the city's own rainfall record into a single umbrella verdict.
| Factor | Weight | What it measures |
|---|---|---|
| Hourly probability | 40% | Peak and sustained chance of measurable rain across the next 24 hours. |
| Expected volume | 30% | Total millimetres, which separates a passing shower from a genuine soaking. |
| Timing & duration | 20% | When rain starts, when it eases, and the longest continuous dry window. |
| Local rain type | 10% | Drizzle, brief showers, thunderstorms or monsoon — each needs different gear. |
Live hourly values come from Open-Meteo and refresh through the day. Monthly rainfall figures are climate normals, so they describe a typical year rather than a forecast.
St Louis records rain on roughly 107 days a year — about a 29% chance on any given day — totalling around 1042mm.
May, with about 108mm over 12 rain days. That is 10% of the entire year's rainfall in a single month.
January is the driest month at 48mm across roughly 5 days. September and October offer dry, comfortable conditions.
St. Louis sits in the Mississippi River corridor — severe thunderstorms and tornadoes are a spring/summer concern. The Gateway Arch is a perfect rainy-day visit.
No. Probability is the chance that at least 0.2mm of rain falls at your location at some point in the period. Check the expected millimetres alongside it: 40% with 0.4mm is a passing shower, 40% with 12mm is a soaking.