Saturday in St. Louis is forecast to start near 63 degrees, with a high around 72. Light showers are possible Saturday morning in parts of northeast Missouri and west-central Illinois; skies in St. Louis are expected to remain mostly cloudy afterward, with light east winds. The outlook lists no watches, warnings or advisories for the area, according to the National Weather Service.
The forecast turns warmer and brighter into the start of the week: Sunday is expected to reach about 77 degrees, followed by a low near 58; Monday is sunny with a high near 78, and Tuesday is mostly sunny with a high around 82. Rain could return after 1 a.m. Tuesday night, with showers and thunderstorms in the outlook Wednesday and likely Thursday; Thursday’s rain chance is 60%, the NWS forecast says.
The warmup sits between two different rainfall snapshots
The forecast high near 82 is above the National Weather Service St. Louis September normal high of 81.1 degrees, but far below the local September record high of 102, set on Sept. 29, 1953, according to the NWS September calendar. The same calendar lists a normal September low of 60.9 degrees.
Rainfall figures offer a separate perspective, but they describe different periods and places. The NWS’s Sept. 25 St. Louis climate report recorded 1.31 inches of precipitation for the month to date, 1.19 inches below the 2.50-inch normal. By contrast, Drought.gov describes January through August 2026 as St. Louis County’s wettest year to date in 132 years. The first figure is a September-to-date observation for St. Louis; the second covers eight months and St. Louis County, so they are not contradictory measures of the same period.
A precipitation probability does not specify how long rain will last or how much of the metro area will receive it. As Statesman.com explains, the percentage concerns the chance of rain at a particular location during the forecast period. The outlook gives no rain totals, so the timing and amount of any midweek rain remain uncertain.
When outdoor plans look most favorable
Saturday’s forecast leaves the later hours mostly cloudy after the early shower chance, while Monday and Tuesday are the clearest and warmest days in the outlook. Rain chances increase after Tuesday night, but the forecast does not establish how long rain will last or where it will fall.
