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Climate · Keystone

Keystone in September

Warm and mostly dry, as the days shorten.

Typical weather, averaged over 30 years

September in Keystone is warm: highs near 75°F, lows near 51°F. Rain falls on about two days a week, and the days shorten by 1 hour 5 minutes from the first week to the last.September in Keystone is warm: highs near 24°C, lows near 11°C. Rain falls on about two days a week, and the days shorten by 1 hour 5 minutes from the first week to the last.

High
75°F24°Caverage
Low
51°F11°Caverage
Wet days
2a week · 30% of days
Daylight
12h 25mon average

Is September a good time to visit Keystone?

Yes. September is one of Keystone's best months (September).

How we judge it: every month is scored on how close its typical high comes to the range from 70°F to 80°F, how mild its nights are, and how rarely it rains. The best months are the run of months that scores best.How we judge it: every month is scored on how close its typical high comes to the range from 21°C to 27°C, how mild its nights are, and how rarely it rains. The best months are the run of months that scores best.

How September sits in the year

week by week

Temperature

Highs near 75°F in September, against 38°F to 84°F through the year.Highs near 24°C in September, against 3°C to 29°C through the year.

Chance of a wet day

30% of days in September, against 16% to 57% through the year.

Cloud cover

33% cover in September, against 27% to 54% through the year.

Daylight

12h 25m in September, against 8h 57m to 15h 25m through the year.

Week by week, lightly smoothed, with September shaded. The olive line marks the best months. Hover or tap a week for its figures.

Either side

  1. August82°28°low 59°low 15°3 wet days a weekRain on about three days a week.
  2. September75°24°low 51°low 11°2 wet days a weekRain on about two days a week.
  3. October62°17°low 40°low 4°2 wet days a weekRain on about two days a week.

Where Keystone sits, in September

America/Denver
this place
typical high in September 40°F4°C95°F35°C
Sunrise, mid-September
6:32 AMsets 7:07 PM
Above the sea
1,430 mupland
Latitude
43.9°Nnorthern hemisphere
Nearest of ours
Saratoga386 km south-west

The land around Keystone, shaded by its typical high in September, the planning map's own layer. Hover the map for the figure at that spot; tap it on a phone. Clock times are local, for the 15th.

Elsewhere in United States in September

high · low · wet days
See September on the planning mapThe whole year in Keystone

Typical weather, averaged over 30 years (1995–2024), from the 11 km grid square nearest Keystone. Temperatures are adjusted against 66 weather stations: daytime highs read about 3.1°F cold in the source data and are raised to match.Temperatures are adjusted against 66 weather stations: daytime highs read about 1.7°C cold in the source data and are raised to match. Daylight is calculated from latitude. Charts are lightly smoothed week to week; the figures in the table are not. Source: Copernicus ERA5-Land reanalysis; cloud cover from NASA's MERRA-2 reanalysis, on a coarser grid of about 50 km. Contains modified Copernicus Climate Change Service information 2026; neither the European Commission nor ECMWF is responsible for any use of it. These are averages, not a forecast.

Daylight is calculated from latitude. Charts are lightly smoothed week to week; the figures in the table are not.

Source: Copernicus ERA5-Land reanalysis; cloud cover from NASA's MERRA-2 reanalysis, on a coarser grid of about 50 km. Contains modified Copernicus Climate Change Service information 2026; neither the European Commission nor ECMWF is responsible for any use of it. These are averages, not a forecast.