Fort Collins, CO weather in September
Fort Collins is mild in September, with some rain: highs average 77°F and nights drop to about 48°F. Rain or snow falls on about 7 days. Snowfall averages about 0.7 in. A good month for most outdoor plans.
- Normal high
- 77°F
- Normal low
- 48°F
- Wet days
- 7
- 1.4 in total
- Snowfall
- 0.7 in
- normal snowfall
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 82°F | 71°F |
| Normal low | 53°F | 42°F |
| Chance of a wet day | 25% | 22% |
| Sunrise / sunset | 6:27 am / 7:33 pm | 6:55 am / 6:44 pm |
| Daylight | 13.1 h | 11.8 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Mountain Time).
A typical September day
- 6 am53°Fdew point 40°F
- 9 am65°Fdew point 40°F
- Noon74°Fdew point 37°F
- 3 pm77°Fdew point 36°F
- 6 pm69°Fdew point 38°F
- 9 pm60°Fdew point 40°F
NOAA hourly normals (local standard time) from Denver Intl Airport (57 mi away); average wind 9 mph; clear or few clouds in 70% of daytime hours, mostly cloudy or overcast in 23%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F14 of 30
- Hot dayshigh 90°F or more2 of 30
- Muggy daysdaily mean dew point 65°F or more0 of 30
- Wet daysat least 0.01 in of rain or melted snow7 of 30
- Notable rainat least 0.10 in3 of 30
- Freezing nightslow 32°F or below1 of 30
- Snow on the groundsnow depth 1 in or more0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain and snow in September
Normal precipitation is 1.4 in; a dry September brings about 0.5 in and a wet one about 2.1 in (25th and 75th percentiles). About 1 day brings half an inch or more. Normal snowfall is 0.7 in.
How September varies from year to year
- Warmest September, 1991-20202015: average high 83°F
- Coolest September1999: average high 72°F
- Wettest September2013: 6.1 in
- Driest September1992: 0.02 in
- Highest reading99°F (September 6, 2020)
- Lowest reading24°F (September 22, 1995)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 85°F | 77°F | 64°F |
| Normal low | 57°F | 48°F | 36°F |
| Wet days | 9 | 7 | 6 |
| Comfortable days | 6 | 14 | 14 |
| Daylight | 13.7 h | 12.5 h | 11.1 h |
Highs change by -8°F from August and -13°F into October.
Nearby alternatives in September
- Warmer: Pueblo, CO163 mi · high 83°F · 5 wet days
- Cooler: Estes Park, CO27 mi · high 70°F · 9 wet days
How Fort Collins ranks in September
- Normal high235th warmest of 378 cities; 7th of 17 in Colorado
- Wet days160th driest of 378
- Comfortable days105th most of 342
What to pack for Fort Collins in September
- Layers – afternoons near 77°F but nights near 48°F
Heating and cooling
September has 120 heating degree days and 51 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Fort Collins in September?
The normal high is 77°F and the normal low is 48°F. From 1991 to 2020 the hottest September reading was 99°F (most recently on September 6, 2020).
Does it rain a lot in Fort Collins in September?
About 7 days in September have at least 0.01 in of precipitation, and the normal total is 1.4 in. The wettest September in 1991-2020 was in 2013 (6.1 in); the driest was in 1992 (0.02 in).
Does it snow in Fort Collins in September?
Yes. Normal snowfall in September is 0.7 in.
Is September a good time to visit Fort Collins?
September ranks 3rd of 12 months on our comfort score for Fort Collins (68 out of 100). It has about 14 comfortable days and about 2 days at 90°F or hotter. The best month is May.
Where the numbers come from
- Temperature, rain, snowfall, snow depth and frost dates: Ft Collins (USC00053005), 0.6 mi S of the city center, 5,004 ft . NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour: Denver Intl Airport (USW00003017), 57 mi SSE of the city center, 5,414 ft (410 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Cloud cover: Cheyenne (USW00024018), 42 mi NNE of the city center, 6,128 ft (1,124 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Denver International Airport (725650-03017), 56 mi SSE of the city center, 5,404 ft (400 ft higher than the city). Hourly observations, 1991-2020.