September weather forecastGrantsdale, MT
September
Weather in September
September, the first month of the autumn in Grantsdale, is still a refreshing month, with an average temperature ranging between max 66.2°F (19°C) and min 39.9°F (4.4°C).Temperature
The move into September indicates a reduction in the average high-temperature, down from August's warm 76.3°F (24.6°C) to a refreshing 66.2°F (19°C). Grantsdale, during the nights of September, registers a substantial plunge from the daytime high, averaging at an icy 39.9°F (4.4°C).Humidity
In Grantsdale, the average relative humidity in September is 57%.Rainfall
In Grantsdale, in September, during 9.9 rainfall days, 0.98" (25mm) of precipitation is typically accumulated. Throughout the year, there are 163.6 rainfall days, and 20.83" (529mm) of precipitation is accumulated.Snowfall
January through May, September through December are months with snowfall. September is the first month it typically snows. Throughout September, in the average 0.4 snowfall days, it receives 0.55" (14mm) of snow. In Grantsdale, during the entire year, snow falls for 101.1 days and aggregates up to 59.17" (1503mm) of snow.Daylight
In Grantsdale, the average length of the day in September is 12h and 31min.On the first day of the month, sunrise is at 6:58 am and sunset at 8:14 pm. On the last day of September, sunrise is at 7:34 am and sunset at 7:17 pm MDT.
Sunshine
In September, the average sunshine is 9.5h.UV index
In September, the average daily maximum UV index is 3. A UV Index of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to UV radiation for the average person.Note: The maximum UV index of 3 during September leads to these instructions:
Prioritize safety - The need to safeguard skin and eyes from harm is emphasized. Limiting sun exposure during midday hours helps in reducing the harmful effects of UV radiation. To cut down UV radiation exposure by about half, sport a wide-brim hat. On your guard! Snow's reflection can almost double the intensity of the Sun's UV radiation.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Grantsdale, MT
- Average high temperature in September: 66.2°F
The warmest month (with the highest average high temperature) is July (77°F).
The month with the lowest average high temperature is December (26.8°F).
- Average low temperature in September: 39.9°F
The month with the highest average low temperature is August (46.9°F).
The coldest month (with the lowest average low temperature) is December (14°F).
Average pressure in September
Grantsdale, MT
- Average pressure in September: 29.99"Hg
The month with the highest atmospheric pressure is January (30.21"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in September
Grantsdale, MT
- Average wind speed in September: 4.4mph
The windiest month (with the highest average wind speed) is January (5.3mph).
The calmest month (with the lowest average wind speed) is August (4.1mph).
Average humidity in September
Grantsdale, MT
- Average humidity in September: 57%
The month with the highest relative humidity is January (89%).
The month with the lowest relative humidity is August (50%).
Average rainfall in September
Grantsdale, MT
- Average rainfall in September: 0.98"
The wettest months (with the highest rainfall) are February and April (2.36").
The driest month (with the least rainfall) is August (0.75").
Average rainfall days in September
Grantsdale, MT
- Average rainfall days in September: 9.9 days
The month with the highest number of rainy days is May (19.5 days).
The month with the least rainy days is July (8 days).
Average snowfall in September
Grantsdale, MT
- Average snowfall in September: 0.55"
The month with the highest snowfall is February (13.03").
The months with the least snowfall are June, July and August (0").
Average snowfall days in September
Grantsdale, MT
- Average snowfall days in September: 0.4 days
The month with the highest number of snowfall days is February (19.3 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Grantsdale, MT
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 42min).
The month with the shortest days is December (Average daylight: 8h and 42min).
- Average sunshine in September: 9h and 30min
The months with the most sunshine are July and August (Average sunshine: 11h and 42min).
The months with the least sunshine are January and December (Average sunshine: 5h and 24min).
Average sunshine days in September
Grantsdale, MT
- Average sunshine days in September: 16.1 days
The month with the most sunshine days is July (18.9 days).
The month with the least sunshine days is February (5.6 days).
Average UV index in September
Grantsdale, MT
- Average UV index in September: 3
The month with the highest UV index is July (UV index 5).
The months with the lowest UV index are February and December (UV index 1).
Average cloud cover in September
Grantsdale, MT
- Average cloud cover in September: 21
The month with the most cloud cover is February (Cloud cover 51).
The month with the least cloud cover is August (Cloud cover 13).
Average visibility in September
Grantsdale, MT
- Average visibility in September: 6mi
The months with the highest visibility are May, June, July, August, September and October (6mi).
The months with the lowest visibility are January, February, March and December (4mi).
