Early autumn · Weather & things to do
Downtown St. Louis & the Arch in September
Downtown St. Louis & the Arch cools off: highs slip to 81°F (27°C), from 87°F in August, with lows of 59°F (15°C) and about 3.1 in (80 mm) of rain.
September opens the best stretch on our comfort score, at 90/100 (the top score of the year).
- Avg high
- 81°F (27°C)
- Avg low
- 59°F (15°C)
- Rain
- 3.1 in (80 mm)
- Humidity
- 70%
- Cloud cover
- 43%
- Daylight
- ~12 h 14 min
- Comfort score
- 90/100 · Great
What September feels like
Days are warm, averaging 81°F (27°C), easy weather for being outside from morning to evening.
There's a big swing between day and night, about 12°C (22°F), so mornings and evenings feel much cooler than the afternoon.
Showers are part of the month, adding up to about 3.1 in (80 mm).
Plan around September
September is one of Downtown St. Louis & the Arch's best months on the climate data.
- Last warm month for a while: October highs fall to 68°F.
- Opens the best-scoring stretch on our comfort score: September & October.
- Comfort improves from 72/100 in August to 90/100.
- Our St. Louis New Year's Eve route is planned for Dec 30 – Jan 1, a window set by the holiday season rather than the weather — September falls outside it.
What to pack for September
- Light, breathable clotheshighs average 81°F
- A warm layer for eveningsnights drop to 59°F
- Packable rain jacket or umbrellaa shower or two is likely
- Comfortable walking shoesmost picks involve some walking
What to do in Downtown St. Louis & the Arch in September
September is good outdoor weather here, so these picks lean toward the open air.
Grand Hall at Union Station
Barrel-vaulted 1894 lobby of the old train station, now a bar with a light show projected on the ceiling.
Gateway Arch National Park
The 630-foot steel arch on the riverfront, with a tram to an observation room at the top and a museum below.
Kiener Plaza
Downtown plaza facing the Old Courthouse and the Arch, home of the free Winterfest Neon Nights party on Dec 31.
Why now September scores 90/100 for comfort, good conditions for being outside.
Crown Candy Kitchen
Soda fountain open since 1913 in Old North St. Louis, known for BLTs, malts and house-made chocolates.
Nearby in September
- Springfield in September~195 mi · highs 81°F, 3.8 in rain · similar daytime temperatures, wetter
- Branson in September~215 mi · highs 84°F, 3.7 in rain · 2°C (3°F) warmer by day, about as wet
- Indianapolis in September~230 mi · highs 78°F, 3.2 in rain · 2°C (3°F) cooler by day, about as wet
- Broad Ripple in September~233 mi · highs 78°F, 3.2 in rain · 2°C (3°F) cooler by day, about as wet
These averages also cover Forest Park & the Central West End.
NASA POWER 2001–2025 monthly averages on a ~50 km grid. Comfort scores weigh temperature, rain, humidity and cloud: see how we score each month. Check a forecast before you go.
Downtown St. Louis & the Arch in September: quick answers
Is September a good time to visit Downtown St. Louis & the Arch?
Yes. On the climate data it's one of the best months, scoring 90/100. Expect highs of 81°F (27°C) and 3.1 in (80 mm) of rain.
How hot is Downtown St. Louis & the Arch in September?
Average highs are 81°F (27°C) and average lows 59°F (15°C), making it the 4th-warmest month by daytime highs.
Does it rain a lot in Downtown St. Louis & the Arch in September?
Some: about 3.1 in (80 mm) of rain falls across September on average, the 4th-driest month of the year. The annual total is about 43.5 in (1106 mm).
What should I pack for Downtown St. Louis & the Arch in September?
Bring light, breathable clothes (highs average 81°F), a warm layer for evenings (nights drop to 59°F), packable rain jacket or umbrella (a shower or two is likely) and comfortable walking shoes (most picks involve some walking).
More on Downtown St. Louis & the Arch
Planning Downtown St. Louis & the Arch in September?
Plan it together in TripsCircle: one itinerary, one shared packing list and costs split as you go.