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
The onset of September in West Yellowstone results in a decrease in the average high-temperature, receding from a pleasant 71.4°F (21.9°C) in August to an enjoyable 61.9°F (16.6°C). West Yellowstone records a significant temperature drop in September nights, lowering to an average of 37.6°F (3.1°C).Humidity
In September, the average relative humidity in West Yellowstone is 57%.Rainfall
In September, the rain falls for 10.5 days. Throughout September, 1.57" (40mm) of precipitation is accumulated. Throughout the year, there are 109.2 rainfall days, and 23.15" (588mm) of precipitation is accumulated.Snowfall
January through July, September through December are months with snowfall in West Yellowstone. September is the first month it typically snows in West Yellowstone. Throughout September, in the average 2.4 snowfall days, it receives 3.27" (83mm) of snow. In West Yellowstone, during the entire year, snow falls for 159.3 days and aggregates up to 120.47" (3060mm) of snow.Daylight
The average length of the day in September in West Yellowstone is 12h and 30min.On the first day of the month, sunrise is at 6:47 am and sunset at 8:00 pm. On the last day of September, sunrise is at 7:22 am and sunset at 7:06 pm MDT.
Sunshine
In September, the average sunshine is 9.8h.UV index
In September, the average daily maximum UV index is 2. A UV Index of 2, and less, symbolizes a minimal health hazard from exposure to the Sun's UV radiation for the ordinary person.Note: In September, the maximum UV index of 2 transforms into these recommendations:
Children, infants, and individuals with sensitive skin should be constantly protected from extended sun exposure. The most potent solar radiation is around mid-day, so one should minimize exposure to direct sunlight during this period. Tightly woven clothing, when worn loosely, shields effectively against the Sun. Notice! The UV radiation of the Sun can be intensified nearly twofold due to the reflective quality of snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the temperature in September in West Yellowstone?
What is the average humidity in September in West Yellowstone?
How many days does it rain in September in West Yellowstone?
When does it start snowing in West Yellowstone?
How many hours of daylight does West Yellowstone have in September?
When is the sunrise / sunset in September in West Yellowstone?
How long on average sun shines in September in West Yellowstone?
How high is the UV index in September in West Yellowstone?
Average temperature in September
West Yellowstone, MT
- Average high temperature in September: 61.9°F
The warmest month (with the highest average high temperature) is July (72.9°F).
The month with the lowest average high temperature is December (20.1°F).
- Average low temperature in September: 37.6°F
The month with the highest average low temperature is August (43.7°F).
The coldest month (with the lowest average low temperature) is December (4.8°F).
Average pressure in September
West Yellowstone, MT
- Average pressure in September: 29.99"Hg
The month with the highest atmospheric pressure is January (30.24"Hg).
The month with the lowest atmospheric pressure is June (29.92"Hg).
Average wind speed in September
West Yellowstone, MT
- Average wind speed in September: 6mph
The windiest month (with the highest average wind speed) is June (6.8mph).
The calmest month (with the lowest average wind speed) is August (5.8mph).
Average humidity in September
West Yellowstone, MT
- Average humidity in September: 57%
The month with the highest relative humidity is February (95%).
The month with the lowest relative humidity is August (50%).
Average rainfall in September
West Yellowstone, MT
- Average rainfall in September: 1.57"
The wettest month (with the highest rainfall) is May (2.8").
The driest month (with the least rainfall) is July (0.91").
Average rainfall days in September
West Yellowstone, MT
- Average rainfall days in September: 10.5 days
The month with the highest number of rainy days is May (17.4 days).
The month with the least rainy days is January (2.2 days).
Average snowfall in September
West Yellowstone, MT
- Average snowfall in September: 3.27"
The month with the highest snowfall is February (17.83").
The month with the least snowfall is August (0").
Average snowfall days in September
West Yellowstone, MT
- Average snowfall days in September: 2.4 days
The month with the highest number of snowfall days is March (24.4 days).
The months with the least snowfall days are July and August (0.2 days).
Average daylight in September /
Average sunshine in September
West Yellowstone, MT
- Average daylight in September: 12h and 3min
The month with the longest days is June (Average daylight: 15h and 30min).
The month with the shortest days is December (Average daylight: 8h and 54min).
- Average sunshine in September: 9h and 5min
The month with the most sunshine is July (Average sunshine: 11h and 48min).
The months with the least sunshine are January, February and December (Average sunshine: 3h and 18min).
Average sunshine days in September
West Yellowstone, MT
- Average sunshine days in September: 14.7 days
The months with the most sunshine days are July and September (14.7 days).
The month with the least sunshine days is February (5.3 days).
Average UV index in September
West Yellowstone, MT
- Average UV index in September: 2
The month with the highest UV index is July (UV index 5).
The months with the lowest UV index are January, February, March, April, October, November and December (UV index 1).
Average cloud cover in September
West Yellowstone, MT
- Average cloud cover in September: 22
The month with the most cloud cover is February (Cloud cover 76).
The month with the least cloud cover is July (Cloud cover 16).
Average visibility in September
West Yellowstone, MT
- Average visibility in September: 6mi
The months with the highest visibility are June, July, August and September (6mi).
The months with the lowest visibility are January, February, March and December (3mi).
West Yellowstone, Montana, USA
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