Monthly climate guide
Aspen weather in September
Expect mild weather in Aspen in September: afternoons reach about 16°C (61°F), while nights drop to around 1°C (34°F). Around 41 mm of rain falls over the month (fairly dry), and skies are a mix of sun and cloud. Daytime highs are 4°C cooler than August and 8°C warmer than October.
What stands out in September
- In Aspen, September is early autumn.
- Evenings cool off sharply: the daily range is around 15°C, so pack a layer.
- Skies are at their clearest this time of year.
- It cools down fast from here: October is about 8°C cooler.
Avg high
16°C
61°F
Avg low
1°C
34°F
Rainfall
41 mm
fairly dry
Humidity
57%
relative
Sky
43%
cloud · a mix of sun and cloud
Aspen weather by month
Show the monthly averages as a table
| Month | Avg high | Avg low | Rain | Humidity | Cloud cover |
|---|---|---|---|---|---|
| January | -6°C / 20°F | -18°C / 0°F | 51 mm | 90% | 56% |
| February | -6°C / 20°F | -18°C / -1°F | 48 mm | 95% | 64% |
| March | -2°C / 29°F | -14°C / 7°F | 48 mm | 89% | 61% |
| April | 3°C / 38°F | -8°C / 17°F | 53 mm | 75% | 67% |
| May | 10°C / 49°F | -4°C / 25°F | 48 mm | 65% | 62% |
| June | 18°C / 65°F | 2°C / 35°F | 16 mm | 49% | 43% |
| July | 21°C / 70°F | 6°C / 42°F | 46 mm | 59% | 53% |
| August | 20°C / 67°F | 5°C / 41°F | 42 mm | 58% | 52% |
| September | 16°C / 61°F | 1°C / 34°F | 41 mm | 57% | 43% |
| October | 8°C / 46°F | -5°C / 24°F | 37 mm | 62% | 47% |
| November | 0°C / 33°F | -11°C / 12°F | 40 mm | 74% | 50% |
| December | -6°C / 21°F | -17°C / 1°F | 47 mm | 86% | 58% |
What to pack for September
- A warm sweater or fleece for layering
- A mid-weight jacket
- An extra layer — evenings are noticeably cooler than afternoons
- A small travel umbrella, just in case
Is September a good time to visit Aspen?
Compare the months in the chart above to find your ideal window.
Best time to visit Aspen →Other United States cities in September
Cite or embed this data
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Aspen weather in September. WeatherCompare, 2026 (NASA POWER / ERA5, 2011–2020 monthly averages). https://weathercompare.eu/weather/usa/aspen/september
<a href="https://weathercompare.eu/weather/usa/aspen/september">Aspen weather in September</a> (WeatherCompare)
<iframe src="https://weathercompare.eu/embed/usa/aspen" width="300" height="160" style="border:0;border-radius:12px" loading="lazy" title="Aspen weather in September"></iframe> <p style="font-size:12px"><a href="https://weathercompare.eu/weather/usa/aspen/september">Aspen weather in September</a> – WeatherCompare</p>
Aspen in September: quick answers
Is September a good time to visit Aspen?
September is a reasonable time for Aspen: highs around 16°C and about 41 mm of rain, though not one of the three best months.
How warm is Aspen in September?
Average highs are about 16°C (61°F) and average lows about 1°C (34°F), based on 10 years of daily data.
Does it rain a lot in Aspen in September?
Aspen typically gets around 41 mm of rain in September — fairly dry.
Figures are long-term averages for the area around Aspen (NASA POWER / ERA5, 2011–2020), not a forecast for a specific year. For upcoming days, see the live multi-source forecast.