September weather forecastHalfmoon, MT
September
Weather in September
The first month of the autumn, September, is still a refreshing month in Halfmoon, Montana, with an average temperature varying between 65.5°F (18.6°C) and 39.2°F (4°C).Temperature
The arrival of September corresponds with a reduction in the average high-temperature, down from August's warm 76.8°F (24.9°C) to a comfortable 65.5°F (18.6°C). Halfmoon observes a dramatic plunge from daytime highs in September, settling at an average low-temperature of 39.2°F (4°C).Humidity
In September, the average relative humidity is 64%.Rainfall
In Halfmoon, in September, it is raining for 8.5 days, with typically 0.71" (18mm) of accumulated precipitation. Throughout the year, there are 126.4 rainfall days, and 11.22" (285mm) of precipitation is accumulated.Snowfall
Months with snowfall are January through May, September through December. September is the first month it typically snows. Throughout September, in the average 0.3 snowfall days, it receives 0.04" (1mm) of snow. In Halfmoon, Montana, during the entire year, snow falls for 97 days and aggregates up to 33.86" (860mm) of snow.Daylight
In September, the average length of the day is 12h and 34min.On the first day of the month, sunrise is at 6:55 am and sunset at 8:17 pm. On the last day of September, sunrise is at 7:36 am and sunset at 7:17 pm MDT.
Sunshine
In September, the average sunshine is 9.4h.UV index
In September, the average daily maximum UV index is 3. A UV Index estimate of 3 to 5 represents a moderate threat to health from exposure to the Sun's UV radiation for ordinary individuals.Note: The UV index of 3 in September translates into these instructions:
Heed the precautions - Suggestions to avoid sunburn are made. Limiting exposure to the direct Sun during midday hours can help prevent harmful UV radiation effects. Sunglasses that ward off UVA and UVB rays play a pivotal role in reducing solar eye damage. Mind this! Nearly twice the UV radiation from the Sun can be reflected by the snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Halfmoon, MT
- Average high temperature in September: 65.5°F
The warmest month (with the highest average high temperature) is July (77.9°F).
The month with the lowest average high temperature is December (25.7°F).
- Average low temperature in September: 39.2°F
The month with the highest average low temperature is August (45.5°F).
The coldest month (with the lowest average low temperature) is February (13.5°F).
Average pressure in September
Halfmoon, MT
- Average pressure in September: 29.97"Hg
The month with the highest atmospheric pressure is January (30.16"Hg).
The month with the lowest atmospheric pressure is June (29.91"Hg).
Average wind speed in September
Halfmoon, MT
- Average wind speed in September: 3.8mph
The windiest month (with the highest average wind speed) is April (4.6mph).
The calmest months (with the lowest average wind speed) are August and December (3.7mph).
Average humidity in September
Halfmoon, MT
- Average humidity in September: 64%
The month with the highest relative humidity is January (93%).
The month with the lowest relative humidity is August (55%).
Average rainfall in September
Halfmoon, MT
- Average rainfall in September: 0.71"
The wettest month (with the highest rainfall) is June (1.42").
The driest month (with the least rainfall) is August (0.43").
Average rainfall days in September
Halfmoon, MT
- Average rainfall days in September: 8.5 days
The month with the highest number of rainy days is April (15.8 days).
The month with the least rainy days is August (6.3 days).
Average snowfall in September
Halfmoon, MT
- Average snowfall in September: 0.04"
The month with the highest snowfall is January (7.72").
The months with the least snowfall are June, July and August (0").
Average snowfall days in September
Halfmoon, MT
- Average snowfall days in September: 0.3 days
The month with the highest number of snowfall days is December (19.1 days).
The months with the least snowfall days are July and August (0 days).
Average daylight in September /
Average sunshine in September
Halfmoon, MT
- Average daylight in September: 12h and 36min
The month with the longest days is June (Average daylight: 16h and 0min).
The month with the shortest days is December (Average daylight: 8h and 24min).
- Average sunshine in September: 9h and 24min
The month with the most sunshine is July (Average sunshine: 11h and 54min).
The month with the least sunshine is January (Average sunshine: 3h and 30min).
Average sunshine days in September
Halfmoon, MT
- Average sunshine days in September: 19 days
The month with the most sunshine days is July (21.5 days).
The month with the least sunshine days is March (7.7 days).
Average UV index in September
Halfmoon, MT
- Average UV index in September: 3
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 1).
Average cloud cover in September
Halfmoon, MT
- Average cloud cover in September: 24
The month with the most cloud cover is January (Cloud cover 65).
The months with the least cloud cover are July and August (Cloud cover 15).
Average visibility in September
Halfmoon, MT
- Average visibility in September: 6mi
The months with the highest visibility are May, June, July, August, September and October (6mi).
The month with the lowest visibility is January (3mi).
