September weather forecastSun Valley, ID
September
Weather in September
September marks the onset of autumn in Sun Valley, bringing a milder and less intense heat than the preceding summer months. Temperatures fall from the highs of 73.2°F (22.9°C) in August to a more temperate 63.7°F (17.6°C). The shift in weather also reduces the heat intensity, paving the way for more comfortable outdoor recreation. Nevertheless, the shortage of daylight hours compared to the summer period is not substantial enough to dampen the city's appeal. Overall, September's weather creates a pleasant amalgamation of the warm summer end and the cool introduction of autumn.Temperature
September in Sun Valley, Idaho, involves a decrease in temperature, down from an agreeable 73.2°F (22.9°C) in August to an enjoyable 63.7°F (17.6°C). In the month of September, Sun Valley witnesses a consistent average low-temperature of 43.2°F (6.2°C).Humidity
The average relative humidity in September in Sun Valley, Idaho, is 44%.Rainfall
In Sun Valley, in September, during 8.8 rainfall days, 0.87" (22mm) of precipitation is typically accumulated. In Sun Valley, during the entire year, the rain falls for 107.7 days and collects up to 15.63" (397mm) of precipitation.Snowfall
January through June, September through December are months with snowfall. September is the first month it typically snows in Sun Valley. Throughout September, in the average 0.5 snowfall days, it receives 0.55" (14mm) of snow. Throughout the year, there are 88.2 snowfall days, and 69.45" (1764mm) of snow is accumulated.Daylight
In September, the average length of the day in Sun Valley is 12h and 29min.On the first day of September in Sun Valley, sunrise is at 7:01 am and sunset at 8:12 pm. On the last day of the month, sunrise is at 7:34 am and sunset at 7:19 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 value of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to UV radiation for the ordinary person.Note: The daily high UV index of 3 during September translates into the following recommendations:
Take precautions - Protection against skin and eye damage is obliged. The Sun is at its harshest during midday; protect yourself by staying in shaded areas and minimizing exposure. During bright days, sunglasses that offer UVA and UVB defense are recommended. Alert! The snow's reflection can amplify the UV radiation of the Sun nearly twice.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Sun Valley, ID
- Average high temperature in September: 63.7°F
The warmest month (with the highest average high temperature) is July (74.1°F).
The month with the lowest average high temperature is December (25°F).
- Average low temperature in September: 43.2°F
The months with the highest average low temperature are July and August (50.5°F).
The coldest month (with the lowest average low temperature) is January (8.4°F).
Average pressure in September
Sun Valley, ID
- Average pressure in September: 29.95"Hg
The month with the highest atmospheric pressure is January (30.27"Hg).
The month with the lowest atmospheric pressure is June (29.89"Hg).
Average wind speed in September
Sun Valley, ID
- Average wind speed in September: 5.4mph
The windiest month (with the highest average wind speed) is July (6.3mph).
The calmest month (with the lowest average wind speed) is January (4.5mph).
Average humidity in September
Sun Valley, ID
- Average humidity in September: 44%
The month with the highest relative humidity is February (87%).
The month with the lowest relative humidity is August (37%).
Average rainfall in September
Sun Valley, ID
- Average rainfall in September: 0.87"
The wettest month (with the highest rainfall) is March (2.01").
The driest month (with the least rainfall) is July (0.43").
Average rainfall days in September
Sun Valley, ID
- Average rainfall days in September: 8.8 days
The month with the highest number of rainy days is May (14.8 days).
The month with the least rainy days is July (5.9 days).
Average snowfall in September
Sun Valley, ID
- Average snowfall in September: 0.55"
The month with the highest snowfall is February (15").
The months with the least snowfall are July and August (0").
Average snowfall days in September
Sun Valley, ID
- Average snowfall days in September: 0.5 days
The month with the highest number of snowfall days is March (16 days).
The months with the least snowfall days are July and August (0 days).
Average daylight in September /
Average sunshine in September
Sun Valley, ID
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 24min).
The month with the shortest days is December (Average daylight: 9h and 0min).
- Average sunshine in September: 9h and 24min
The month with the most sunshine is July (Average sunshine: 12h and 0min).
The month with the least sunshine is January (Average sunshine: 5h and 42min).
Average sunshine days in September
Sun Valley, ID
- Average sunshine days in September: 19.7 days
The month with the most sunshine days is July (20.8 days).
The month with the least sunshine days is April (11.1 days).
Average UV index in September
Sun Valley, ID
- Average UV index in September: 3
The months with the highest UV index are June and July (UV index 5).
The month with the lowest UV index is February (UV index 1).
Average cloud cover in September
Sun Valley, ID
- Average cloud cover in September: 15
The month with the most cloud cover is February (Cloud cover 44).
The month with the least cloud cover is July (Cloud cover 10).
Average visibility in September
Sun Valley, ID
- Average visibility in September: 6mi
The months with the highest visibility are April, May, June, July, August, September, October and November (6mi).
The months with the lowest visibility are January, February and December (4mi).
