Contents
- Weather in September
- Frequently asked questions
- Average temperature in September
- Average pressure in September
- Average wind speed in September
- Average humidity in September
- Average rainfall in September
- Average rainfall days in September
- Average snowfall in September
- Average snowfall days in September
- Average daylight in September
- Average sunshine in September
- Average sunshine days in September
- Average UV index in September
- Average cloud cover in September
- Average visibility in September
Weather in September
Temperature
September implies a soft temperature shift, with average high-temperatures reducing from August's 84.7°F (29.3°C) to a still moderately hot 77.2°F (25.1°C). Longmont's September nights cool down significantly from the day's heat, to an average low-temperature of 51.1°F (10.6°C).Humidity
In Longmont, the average relative humidity in September is 43%.Rainfall
In Longmont, in September, it is raining for 9.7 days, with typically 0.75" (19mm) of accumulated precipitation. Throughout the year, in Longmont, there are 105.4 rainfall days, and 10.43" (265mm) of precipitation is accumulated.Snowfall
June through September are months without snowfall.Daylight
In Longmont, Colorado, the average length of the day in September is 12h and 26min.On the first day of the month, sunrise is at 6:28 am and sunset at 7:31 pm. On the last day of September, in Longmont, Colorado, sunrise is at 6:56 am and sunset at 6:43 pm MDT.
Sunshine
The average sunshine in September in Longmont is 11h.UV index
In September, the average daily maximum UV index in Longmont is 4. A UV Index value of 3 to 5 symbolizes a medium vulnerability from exposure to the Sun's UV rays for the average person.Note: The UV index of 4 during September leads to these advisories:
Undertake precautions - Guarding against sun damage is counselled. To guard against the harmful effects of the Sun, minimize exposure during midday. A hat with a broad brim is indispensable, filtering out up to half of UV rays. Beware! Reflection from snow can magnify the Sun's UV radiation nearly twofold.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What are September temperatures in Longmont?
What is the average humidity in September in Longmont?
How much does it rain in Longmont in September?
When it does not snow in Longmont?
Does it snow in Longmont in September?
How many hours of daylight does Longmont have in September?
When is the sunrise / sunset in September in Longmont?
How many hours of sunshine does Longmont have in September?
What is the UV index intensity in September in Longmont?
Average temperature in September
Longmont, CO
- Average high temperature in September: 77.2°F
The warmest month (with the highest average high temperature) is July (85.6°F).
The month with the lowest average high temperature is December (39°F).
- Average low temperature in September: 51.1°F
The month with the highest average low temperature is July (59.2°F).
The coldest month (with the lowest average low temperature) is December (19.9°F).
Average pressure in September
Longmont, CO
- Average pressure in September: 30"Hg
The month with the highest atmospheric pressure is January (30.15"Hg).
The months with the lowest atmospheric pressure are April and June (29.91"Hg).
Average wind speed in September
Longmont, CO
- Average wind speed in September: 5.6mph
The windiest months (with the highest average wind speed) are March and April (6.6mph).
The calmest months (with the lowest average wind speed) are August and September (5.6mph).
Average humidity in September
Longmont, CO
- Average humidity in September: 43%
The month with the highest relative humidity is February (66%).
The month with the lowest relative humidity is August (42%).
Average rainfall in September
Longmont, CO
- Average rainfall in September: 0.75"
The wettest month (with the highest rainfall) is May (1.69").
The driest month (with the least rainfall) is January (0.35").
Average rainfall days in September
Longmont, CO
- Average rainfall days in September: 9.7 days
The month with the highest number of rainy days is July (16 days).
The month with the least rainy days is January (3.5 days).
Average snowfall in September
Longmont, CO
- Average snowfall in September: 0"
The month with the highest snowfall is November (4.41").
The months with the least snowfall are June, July, August and September (0").
Average snowfall days in September
Longmont, CO
- Average snowfall days in September: 0.1 days
The month with the highest number of snowfall days is February (7.7 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Longmont, 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 24min).
- Average sunshine in September: 11h and 0min
The month with the most sunshine is June (Average sunshine: 11h and 54min).
The month with the least sunshine is February (Average sunshine: 6h and 48min).
Average sunshine days in September
Longmont, CO
- Average sunshine days in September: 16.5 days
The month with the most sunshine days is January (23.4 days).
The month with the least sunshine days is July (9.3 days).
Average UV index in September
Longmont, CO
- Average UV index in September: 4
The months with the highest UV index are July and August (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).
Average cloud cover in September
Longmont, CO
- Average cloud cover in September: 16
The months with the most cloud cover are April and May (Cloud cover 26).
The months with the least cloud cover are June and September (Cloud cover 16).
Average visibility in September
Longmont, 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).
Longmont, Colorado, USA
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