Weather in St. Louis in August

Shoulder season. August is shoulder season in St. Louis — cheaper, quieter, and a genuine gamble. Highs average 31 °C, lows 19.5 °C, and rain falls on 12 days — nothing in the month is working against you.

August ranks 7 of 12 in St. Louis: past the worst of the year but short of October, which is the month to book if the dates are open.

Rain on 12 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 31 °C days and 19.5 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: 18 days top 30 °C — hot spells arrive, but they break. Across the twenty years measured, the hottest August day reached 40.7 °C and the coldest night fell to 9.7 °C, and the wettest single day dropped 57 mm — roughly 61% of the month's rain in one day.

August is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest August on record still delivered 180 mm against 35 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 93 mm average is a reasonable planning figure, not a promise.

Wind is light at 5.6 km/h, so the temperature on the page is close to the temperature on your skin, and humidity is unremarkable at 71%.

How August sits in the year

Temperatures hold steady either side: 31.2 °C in July, 31 here, 27.6 in September. Nothing about the timing within the month matters much.

Daylight in August

13.7 hours of daylight, losing 1.1 hours across the month. That is between St. Louis's extremes of 14.8 and 9.5 hours, so days are long enough not to constrain the plan.

An inland climate

With no coast nearby, the year swings a fair way — 36.6 °C between the warmest afternoons and the coldest nights, wider than any coastal city at this latitude would manage.

How busy it gets

Busy. Popular without being frantic; book the things you care about, improvise the rest.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

August in St. Louis versus nearby

If St. Louis is one option among several, the nearby comparison is worth making. Indianapolis is a better bet in August — 2.6 °C cooler, the same number of rain days. Kansas City is close enough to be a coin toss — within a degree on temperature, the same number of rain days.

So: August is a compromise. October is 22 points better and is what St. Louis is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in St. Louis

See all twelve months in St. Louis, or where else to go in August.