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
During the transition into September, Decker observes a decrease in the average high-temperature, falling from a warm 83.7°F (28.7°C) in August to a still moderately hot 74.1°F (23.4°C). In September, in Decker, Montana, the average low-temperature is a fresh 52.7°F (11.5°C).Humidity
In September, the average relative humidity in Decker is 44%.Rainfall
In Decker, during September, the rain falls for 8.6 days and regularly aggregates up to 0.83" (21mm) of precipitation. In Decker, during the entire year, the rain falls for 127.6 days and collects up to 14.25" (362mm) of precipitation.Snowfall
January through May, September through December are months with snowfall. September is the first month it typically snows. Throughout September, in the average 0.2 snowfall days, it receives 0.12" (3mm) of snow. Throughout the year, there are 65.3 snowfall days, and 28.82" (732mm) of snow is accumulated.Daylight
In September, the average length of the day is 12h and 31min.On the first day of the month, sunrise is at 6:30 am and sunset at 7:43 pm. On the last day of September, sunrise is at 7:05 am and sunset at 6:49 pm MDT.
Sunshine
In Decker, the average sunshine in September is 10.8h.UV index
The average daily maximum UV index in September is 4. A UV Index estimate of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV radiation for average individuals.Note: In September, a regular UV index of 4 translates into these guidelines:
Ensure safety - Sun damage prevention is strongly urged. Solar radiation is at its peak intensity during midday, so it's advisable to stay indoors or in the shade. Your best bet for sun defense on the face, eyes, and neck is a hat with a wide brim. Be aware! The intensity of the Sun's UV radiation can be amplified nearly twice due to snow reflection.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the temperature in September?
What is the average humidity in September?
How much does it rain in September?
When does it start snowing?
How many hours of daylight does Decker have in September?
What time are sunrise and sunset in September?
How many hours of sunshine does Decker have in September?
What is the UV index intensity in September?
Average temperature in September
Decker, MT
- Average high temperature in September: 74.1°F
The warmest month (with the highest average high temperature) is July (85.5°F).
The month with the lowest average high temperature is December (31.1°F).
- Average low temperature in September: 52.7°F
The month with the highest average low temperature is July (61.5°F).
The coldest months (with the lowest average low temperature) are January and February (16.2°F).
Average pressure in September
Decker, MT
- Average pressure in September: 29.93"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.85"Hg).
Average wind speed in September
Decker, MT
- Average wind speed in September: 7.6mph
The windiest month (with the highest average wind speed) is April (9.1mph).
The calmest months (with the lowest average wind speed) are July and December (6.8mph).
Average humidity in September
Decker, MT
- Average humidity in September: 44%
The months with the highest relative humidity are January and February (79%).
The month with the lowest relative humidity is August (40%).
Average rainfall in September
Decker, MT
- Average rainfall in September: 0.83"
The wettest month (with the highest rainfall) is May (2.64").
The driest month (with the least rainfall) is December (0.67").
Average rainfall days in September
Decker, MT
- Average rainfall days in September: 8.6 days
The month with the highest number of rainy days is May (18 days).
The month with the least rainy days is January (6.3 days).
Average snowfall in September
Decker, MT
- Average snowfall in September: 0.12"
The month with the highest snowfall is February (5.2").
The months with the least snowfall are June, July and August (0").
Average snowfall days in September
Decker, MT
- Average snowfall days in September: 0.2 days
The month with the highest number of snowfall days is February (14.3 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Decker, MT
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 36min).
The month with the shortest days is December (Average daylight: 8h and 48min).
- Average sunshine in September: 10h and 5min
The months with the most sunshine are July and August (Average sunshine: 11h and 54min).
The month with the least sunshine is February (Average sunshine: 5h and 42min).
Average sunshine days in September
Decker, MT
- Average sunshine days in September: 18.2 days
The month with the most sunshine days is September (18.2 days).
The month with the least sunshine days is May (9.6 days).
Average UV index in September
Decker, MT
- Average UV index in September: 4
The month with the highest UV index is July (UV index 7).
The months with the lowest UV index are January, February, March, November and December (UV index 2).
Average cloud cover in September
Decker, MT
- Average cloud cover in September: 18
The month with the most cloud cover is February (Cloud cover 41).
The months with the least cloud cover are July and August (Cloud cover 14).
Average visibility in September
Decker, MT
- 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).
Decker, Montana, USA
Weather forecast for your location
2. Allow the app to use your location