Saint Louis Weather in September

St. Louis at the confluence of the Missouri and Mississippi Rivers has one of America's most oppressive summer climates. The rivers converge here creating maximum humidity, and the city sits in a bowl that traps heat. The 2012 heat wave killed many here, and the Gateway Arch's stainless steel surface is so thermally conductive it can be felt at distance on hot days.

Excellent shoulder season — warm with fewer tourists in many destinations.