St. Louis weather in August
August in St. Louis: sweltering, rainy — a great time to visit.
Updated September 2026 · climate normals from ERA5 reanalysis
#6 of 12 months in St. Louis · #882 of 1413 destinations to visit in August · comfort 73/100 (tier B)
- Days
- 31°C
- Nights
- 19°C
- Wet days
- 8
- Sun
- 11 h
- Humidity
- 71%
- Daylight
- 14 h

Traveller notes on St. Louis in August
Other months in St. Louis
Regulars describe this month as a genuine toss-up rather than a settled pattern - balmy and pleasant one visit, oppressively humid like the Deep South the next, with the odds of the muggier version rising the closer the calendar gets to July. Our row backs the real heat and building humidity, 31.3C reading as a hot 34C at 66 percent humidity, over 18C nights, with 91.3mm of rain across 6.9 days. Regulars comparing this month to August don't find a clear winner on crowds either, both drawing similar numbers, so the honest deciding factor ends up being which version of the heat gamble a visitor is more willing to take. The record: 12 hours of sun, a 14.7 kph wind and AQI 68.
Regulars call April the most beautiful month here for the blossom and new leaves, and immediately qualify it: this is also when storms and rapid weather swings are most likely, chilly evenings alongside daytime warmth, and their standing advice is to check a local forecast a day or two out rather than trust a seasonal average. Our row shows the range that produces - 19.9C over 6.5C, with 109.5mm of rain across 9.1 days and a trace of snow, 0.5cm, still possible early in the month. Spring and autumn are named as this city's best seasons overall, and April earns that with qualifications rather than without them. The record: humidity 64 percent, 9 hours of sun, a 20.6 kph wind and AQI 42.
Locals put October among the best weeks here and give a date for the end of it: the turn usually does not happen until around Halloween, so the month is autumn in colour and late summer in temperature. Our row reads 21.7C by day against 7.7C at night, a fourteen-degree fall that catches people who packed for the afternoon, and the felt figures are 20C and 6C in a 17.2 kph wind. Rain is light and infrequent, 70.8mm across 5.6 days, and the 0.1cm in the snow column is the first hint of the season rather than a forecast. Early October also beats the fall road-trip crowds further out. The record: humidity 66 percent, 7.8 hours of sun and AQI 36.
September is the month St Louis regulars pick alongside May, and their framing is that it improves as it runs: the first week or so can still be properly hot, a hangover from a humid July and August, and the comfort builds week by week, with the last third the part they recommend. Mid-September sits in the low 80s Fahrenheit, though they are careful to add that the odd hot day still jumps up out of nowhere. It is fairly dry by local standards too - our row's 83.1mm falls across only 5.3 days, which is thunderstorm rain rather than drizzle - and that combination is why the outdoor events calendar fills up. The record: 28.9C days that feel like 30C, 14.7C nights, humidity 67 percent and 10.2 hours of sun.
Year-round notes are on St. Louis's overview. Add your own note from St. Louis's card on the map.
St. Louis climate normals — August
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in St. Louis in August
How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.
Peak crowdsJapanese Festival, Summer break in United States, school holidays in 2 of the markets that fill it(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for St. Louis's weather
Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).
Fair weatherSt. Louis's best weather comes in May, September and October — separate windows, not one continuous season.
Best weatherFair weatherToughest weather
What's on in St. Louis in August
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Rule
Arch tram timed tickets
1 Jan – 31 DecBook earlyThe ride to the top of the Arch is sold as a timed slot and the summer and holiday-weekend trams go days ahead. The museum underneath is free and needs no ticket at all. Source ↗
- Hazard
Summer heat and humidity
15 Jun – 5 Sep · usuallyExtreme heatThe river valley traps humidity and the heat index runs well above the thermometer for weeks. Forest Park is a morning walk in July, and the Arch grounds have no shade at all. Source ↗
- Festival
Japanese Festival
30 Aug – 8 Sep · usuallyMajor festivalCrowdedThree days at the Botanical Garden over Labor Day weekend, running since 1977 and one of the largest of its kind in the country. Evening taiko in the Japanese garden is the reason to go. Source ↗
Where is St. Louis?
St. Louis in August — FAQ
- Is August a good time to visit St. Louis?
- August in St. Louis: sweltering, rainy — a great time to visit. It ranks #6 of 12 months for St. Louis on SeasonMap's comfort score (73/100).
- What is the weather like in St. Louis in August?
- In August, St. Louis averages a daily high of 30.8°C and a low of 18.7°C, with about 113.8 mm of rain over roughly 7.6 rainy days.
- What is the air quality in St. Louis in August?
- St. Louis has a mean US Air Quality Index of about 64 in August.