September weather forecastHelena, MT
September
Weather in September
September witnesses the onset of fall in Helena, Montana. The weather begins a gradual cooling with temperatures averaging around 68.2°F (20.1°C). This month marks the transition from the height of summer to the beginnings of autumn. Amidst the crisp air and falling leaves, September still retains warmth during the day, making it a delightful time for outdoor activities. The changing hues of the city offer a picturesque and tranquil experience for both residents and tourists.Temperature
Helena's progression into September includes a drop in the average high-temperature, from a moderately hot 78.1°F (25.6°C) in August to a pleasant 68.2°F (20.1°C). A noticeable downturn in temperature characterizes the September nights, averaging at a frosty 43.9°F (6.6°C).Humidity
In September, the average relative humidity is 51%.Rainfall
In Helena, Montana, in September, it is raining for 8.1 days, with typically 0.94" (24mm) of accumulated precipitation. In Helena, during the entire year, the rain falls for 123.7 days and collects up to 12.4" (315mm) of precipitation.Snowfall
Months with snowfall are January through May, September through December. September is the first month it typically snows in Helena. Throughout September, in the average 0.7 snowfall days, it receives 1.77" (45mm) of snow. In Helena, Montana, during the entire year, snow falls for 80.4 days and aggregates up to 34.88" (886mm) of snow.Daylight
The average length of the day in September is 12h and 32min.On the first day of September in Helena, sunrise is at 6:49 am and sunset at 8:06 pm. On the last day of the month, sunrise is at 7:26 am and sunset at 7:09 pm MDT.
Sunshine
The average sunshine in September in Helena, Montana, is 9.7h.UV index
The average daily maximum UV index in September is 3. A UV Index reading of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV radiation for the average person.Note: In September, a regular UV index of 3 translates into these guidelines:
Ensure safety - Imperative it is to shield skin and eyes from damage. When the Sun is at its strongest around midday, find shade and limit exposure. Counter UV radiation's ill effects with clothing designed for sun safety and UV-resistant eyewear. Mark this! Snow reflection can nearly double the UV radiation intensity from the Sun.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Helena, MT
- Average high temperature in September: 68.2°F
The warmest month (with the highest average high temperature) is July (80.2°F).
The month with the lowest average high temperature is December (27.7°F).
- Average low temperature in September: 43.9°F
The month with the highest average low temperature is July (50.4°F).
The coldest month (with the lowest average low temperature) is December (14.2°F).
Average pressure in September
Helena, MT
- Average pressure in September: 29.98"Hg
The month with the highest atmospheric pressure is January (30.18"Hg).
The month with the lowest atmospheric pressure is June (29.9"Hg).
Average wind speed in September
Helena, MT
- Average wind speed in September: 5.9mph
The windiest month (with the highest average wind speed) is November (7.1mph).
The calmest month (with the lowest average wind speed) is August (5mph).
Average humidity in September
Helena, MT
- Average humidity in September: 51%
The month with the highest relative humidity is January (85%).
The months with the lowest relative humidity are July and August (46%).
Average rainfall in September
Helena, MT
- Average rainfall in September: 0.94"
The wettest month (with the highest rainfall) is June (2.01").
The driest months (with the least rainfall) are January and December (0.63").
Average rainfall days in September
Helena, MT
- Average rainfall days in September: 8.1 days
The month with the highest number of rainy days is May (15.8 days).
The month with the least rainy days is November (7 days).
Average snowfall in September
Helena, MT
- Average snowfall in September: 1.77"
The month with the highest snowfall is February (6.18").
The months with the least snowfall are June, July and August (0").
Average snowfall days in September
Helena, MT
- Average snowfall days in September: 0.7 days
The month with the highest number of snowfall days is February (16.2 days).
The months with the least snowfall days are July and August (0 days).
Average daylight in September /
Average sunshine in September
Helena, MT
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 48min).
The month with the shortest days is December (Average daylight: 8h and 36min).
- Average sunshine in September: 9h and 42min
The month with the most sunshine is July (Average sunshine: 11h and 42min).
The month with the least sunshine is January (Average sunshine: 5h and 36min).
Average sunshine days in September
Helena, MT
- Average sunshine days in September: 19.3 days
The month with the most sunshine days is July (20.5 days).
The month with the least sunshine days is April (9.8 days).
Average UV index in September
Helena, MT
- Average UV index in September: 3
The month with the highest UV index is July (UV index 6).
The month with the lowest UV index is February (UV index 1).
Average cloud cover in September
Helena, MT
- Average cloud cover in September: 22
The month with the most cloud cover is February (Cloud cover 47).
The months with the least cloud cover are July and August (Cloud cover 15).
Average visibility in September
Helena, MT
- Average visibility in September: 6mi
The months with the highest visibility are March, April, May, June, July, August, September, October and November (6mi).
The months with the lowest visibility are January, February and December (5mi).
