Gateway Arch in September: Crowds, Weather & What to Pack
Best window · VisitWhen score 80/100 · #1 of 12 months
September is one of the best months of the year to visit Gateway Arch National Park: crowds run 29% of the July peak (139,931 average visits). Weather: highs average 81°F and lows 57°F, with 3.4″ of precipitation and 12.5 hours of daylight. Computed from NPS and NOAA data.
Crowds in September
Gateway Arch averages 139,931 recreation visits in September — 29% of what July, the peak month, draws. Plan lodging and entries with that in mind.
Weather & daylight
Expect warm days (highs average 81°F), and nights stay mild (lows average 57°F). Average precipitation is 3.4″ for the month. Mid-month daylight runs 12.5 hours.
NOAA 1991–2020 monthly normals, station CAHOKIA ST LOUIS AP, IL US (4 mi from park coordinates, 413 ft elevation) — conditions vary inside the park, especially with elevation. Daylight computed for the 15th of September.
What to pack for Gateway Arch in September
Computed from the month's weather normals above — not a generic list.
- Packable rain jacket — 3.4″ of precipitation is normal this month
- Sturdy broken-in footwear, navigation and a basic first-aid kit — every park, every month
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Also at their best in September
Other parks whose computed September verdict is a best window — same NPS × NOAA formula:
- Wrangell–St. Elias in September — 25% of peak crowds, highs 56°F, score 84/100
- Guadalupe Mountains in September — 35% of peak crowds, highs 80°F, score 81/100
- Isle Royale in September — 39% of peak crowds, highs 65°F, score 79/100
- Crater Lake in September — 49% of peak crowds, highs 63°F, score 77/100
Common questions
Is Gateway Arch crowded in September?
No — September is one of the quieter months: 29% of the July peak, averaging 139,931 visits (NPS, 2021–2025).
What is the weather like in Gateway Arch in September?
Average highs of 81°F, lows of 57°F, 3.4″ of precipitation (NOAA 1991–2020 normals, CAHOKIA ST LOUIS AP, IL US station).
What should I pack for Gateway Arch in September?
Packable rain jacket; Sturdy broken-in footwear, navigation and a basic first-aid kit — the full weather-computed list is on this page.
See also: the best national parks to visit in September · Last verified 2026-09-24