September weather forecast
Fort Collins, CO

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A scenic residential estate in Fort Collins, Colorado
A scenic residential estate in Fort Collins, Colorado

Weather in September

September in Fort Collins brings a noticeable drop in temperature, to a mild 74.5°F (23.6°C), indicating the onset of the fall season. This month marks the transition from the peak summer heat to a much cooler autumn climate. The fall foliage, coupled with cool temperatures, makes the city a picturesque destination. With dryer weather and lesser clouds, it's an ideal time for those seeking to enjoy the outdoors.

Temperature

The arrival of September is marked by a minor reduction in average high-temperature, sliding from a moderately hot 81.5°F (27.5°C) in August to a still warm 74.5°F (23.6°C). In Fort Collins, the average temperature during the nights of September marks a significant drop from the daily high, settling at a frosty 49.3°F (9.6°C).

Humidity

June, August and September, with an average relative humidity of 45%, are the least humid months in Fort Collins.

Rainfall

In Fort Collins, in September, during 6.3 rainfall days, 0.55" (14mm) of precipitation is typically accumulated. Throughout the year, in Fort Collins, there are 73.4 rainfall days, and 7.64" (194mm) of precipitation is accumulated.

Snowfall

In Fort Collins, snow does not fall in June through September.

Daylight

The average length of the day in September is 12h and 27min.
On the first day of September in Fort Collins, sunrise is at 6:28 am and sunset at 7:31 pm. On the last day of the month, sunrise is at 6:56 am and sunset at 6:43 pm MDT.

Sunshine

In Fort Collins, Colorado, the average sunshine in September is 11h.

UV index

In September, the average daily maximum UV index is 4. A UV Index value of 3 to 5 symbolizes a moderate health risk from exposure to the Sun's UV rays for ordinary individuals.
Note: The UV index of 4 in September translates into these instructions:
Be mindful. Individuals with a lighter skin tone may suffer burns in less than 30 minutes. Solar radiation peaks around mid-day, so it's wise to limit exposure to the Sun at this time. A hat with a generous brim can prevent nearly 50% of UV rays from reaching your eyes.
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Frequently asked questions

What is the usual temperature for Fort Collins in September?

September temperatures in Fort Collins, Colorado, vary between a high-temperature of 74.5°F (23.6°C) and a low-temperature of 49.3°F (9.6°C). The average heat index (a.k.a. 'real feel', 'felt air temperature'), which combines air temperature and relative humidity, in August is evaluated at 82.4°F (28°C).

What is the least humid month in Fort Collins?

The months with the lowest humidity in Fort Collins are June, August and September, with an average relative humidity of 45%.

What is the average humidity in September in Fort Collins?

The average relative humidity in September in Fort Collins is 45%.

How much does it rain in Fort Collins in September?

In Fort Collins, in September, during 6.3 rainfall days, 0.55" (14mm) of precipitation is typically accumulated.

When it does not snow in Fort Collins?

June through September are months without snowfall.

Does it snow in Fort Collins in September?

In Fort Collins, in September, it doesn't snow. In October, it regularly snows.

What is the average length of the day in September in Fort Collins?

In September, the average day length is 12h and 27min.

When are sunrise and sunset in September in Fort Collins?

In September, on the first day of the month, sunrise is at 6:28 am and sunset at 7:31 pm. On the last day of the month, in Fort Collins, sunrise is at 6:56 am and sunset at 6:43 pm MDT.

How many hours of sunshine does Fort Collins have in September?

In Fort Collins, Colorado, the average sunshine duration in September is 11h.

What is the UV index intensity in September in Fort Collins?

The average daily maximum UV index in September in Fort Collins is 4. A UV Index reading of 3 to 5 represents a medium hazard to health from unprotected exposure to UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in September
Fort Collins, CO

Average temperature in September - Fort Collins, CO
  • Average high temperature in September: 74.5°F

The warmest month (with the highest average high temperature) is July (82.9°F).
The month with the lowest average high temperature is December (36.1°F).

  • Average low temperature in September: 49.3°F

The month with the highest average low temperature is July (56.8°F).
The coldest month (with the lowest average low temperature) is December (18.7°F).

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Average pressure in September
Fort Collins, CO

Average pressure in September - Fort Collins, CO
  • Average pressure in September: 29.99"Hg

The month with the highest atmospheric pressure is January (30.15"Hg).
The month with the lowest atmospheric pressure is June (29.9"Hg).

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Average wind speed in September
Fort Collins, CO

Average wind speed in September - Fort Collins, CO
  • Average wind speed in September: 6mph

The windiest month (with the highest average wind speed) is April (7.6mph).
The calmest month (with the lowest average wind speed) is August (5.6mph).

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Average humidity in September
Fort Collins, CO

Average humidity in September - Fort Collins, CO
  • Average humidity in September: 45%

The month with the highest relative humidity is February (67%).
The months with the lowest relative humidity are June, August and September (45%).

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Average rainfall in September
Fort Collins, CO

Average rainfall in September - Fort Collins, CO
  • Average rainfall in September: 0.55"

The wettest month (with the highest rainfall) is May (1.5").
The driest month (with the least rainfall) is January (0.12").

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Average rainfall days in September
Fort Collins, CO

Average rainfall days in September - Fort Collins, CO
  • Average rainfall days in September: 6.3 days

The month with the highest number of rainy days is July (14.6 days).
The month with the least rainy days is January (1.2 days).

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Average snowfall in September
Fort Collins, CO

Average snowfall in September - Fort Collins, CO
  • Average snowfall in September: 0"

The month with the highest snowfall is April (3.27").
The months with the least snowfall are June, July, August and September (0").

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Average snowfall days in September
Fort Collins, CO

Average snowfall days in September - Fort Collins, CO
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is February (4.3 days).
The months with the least snowfall days are June, July, August and September (0 days).

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Average daylight in September /
Average sunshine in September
Fort Collins, CO

Average daylight in September / Average sunshine in September - Fort Collins, CO
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 15h and 0min).
The month with the shortest days is December (Average daylight: 9h and 18min).

  • Average sunshine in September: 11h and 0min

The month with the most sunshine is June (Average sunshine: 11h and 48min).
The month with the least sunshine is February (Average sunshine: 6h and 42min).

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Average sunshine days in September
Fort Collins, CO

Average sunshine days in September - Fort Collins, CO
  • Average sunshine days in September: 21.7 days

The months with the most sunshine days are January and December (27.5 days).
The month with the least sunshine days is July (14.9 days).

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Average UV index in September
Fort Collins, CO

Average UV index in September - Fort Collins, CO
  • Average UV index in September: 4

The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).

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Average cloud cover in September
Fort Collins, CO

Average cloud cover in September - Fort Collins, CO
  • Average cloud cover in September: 16

The months with the most cloud cover are February, April and May (Cloud cover 27).
The month with the least cloud cover is September (Cloud cover 16).

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Average visibility in September
Fort Collins, CO

Average visibility in September - Fort Collins, CO
  • Average visibility in September: 6mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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Fort Collins, Colorado, USA

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