This map shows where weather is most comfortable across the United States during September, based on Perfect Weather Index scores averaged across recent years.
Scores combine temperature, sunshine, humidity, and wind to highlight regions that consistently offer the most pleasant outdoor conditions for the month.
September succeeds because it strikes a rare nationwide balance. Summer heat has retreated, humidity drops sharply, storm frequency decreases, and cold air remains largely absent. Unlike spring — which is often volatile — or later fall, which brings cold to northern areas, September offers stability across a broad range of climates simultaneously.
New York and Vermont experience their best weather of the year in September. Cooler nights, mild afternoons, lower humidity, and fewer storms combine to produce consistently high comfort scores across both coastal and inland areas.
Maine builds on its strong August performance and reaches its seasonal peak. Coastal and interior areas both benefit, with far less variability than during summer.
Utah stands out in the West, particularly around Bryce Canyon, where September delivers pleasant daytime temperatures, low humidity, and minimal precipitation — some of the best hiking conditions in the country.
Montana also performs exceptionally well, with high-elevation areas delivering dry, clear, mild conditions before autumn cooling accelerates.
See how all 50 states rank this month →
September is an outstanding month for national parks across all three regions. Mountain parks like Yellowstone and Rocky Mountain offer ideal fall conditions with thinning crowds. Eastern parks like Acadia and the Great Smoky Mountains hit their seasonal peak. Desert parks like the Grand Canyon and Zion become comfortable again after the heat of summer.
(Based on statewide average Perfect Weather Index scores.)
If your goal is the most consistently comfortable weather across the U.S., September is the clear winner. The data supports broad flexibility — almost every region improves — but the Northeast and high-elevation West benefit most. It's also one of the best months of the year for national park visits across all regions.
For a detailed look at how September 2025 specifically played out, see the September 2025 weather recap.
Data Note:
This analysis is based on National Weather Service forecast data and represents modeled conditions, not verified observations. Results reflect relative comfort patterns for September and may vary from year to year.