September weather forecastSpearfish, SD
September
Weather in September
September's weather lays the groundwork for autumn's arrival in Spearfish. At 72.5°F (22.5°C), this transitional month ushers in cooler temperatures without surrendering summer's residual warmth completely. Rainfall takes a slight dip compared to August, marking a slow return to drier conditions. Longer nights and declining temperatures point towards the upcoming fall, while climatic comfort is retained beneath the warm sun. The wind speed falls, leaving a mild breeze that enhances the pleasing fall conditions.Temperature
Onset of September in Spearfish, South Dakota, witnesses a reduction in the average high-temperature, falling from a moderately hot 81.9°F (27.7°C) in August to a pleasant 72.5°F (22.5°C). Spearfish experiences an average low-temperature of 52°F (11.1°C) in month of September.Humidity
In September, the average relative humidity in Spearfish is 50%.Rainfall
In September, in Spearfish, the rain falls for 7.6 days. Throughout September, 0.79" (20mm) of precipitation is accumulated. Throughout the year, in Spearfish, there are 99.6 rainfall days, and 15.63" (397mm) of precipitation is accumulated.Snowfall
January through May, September through December are months with snowfall. September is the first month it typically snows in Spearfish. Throughout September, in the average 0.1 snowfall days, it receives 0.16" (4mm) of snow. Throughout the year, in Spearfish, there are 56.8 snowfall days, and 36.3" (922mm) of snow is accumulated.Daylight
The average length of the day in September is 12h and 30min.On the first day of September, sunrise is at 6:19 am and sunset at 7:31 pm. On the last day of the month, sunrise is at 6:53 am and sunset at 6:37 pm MDT.
Sunshine
The average sunshine in September is 10.6h.UV index
In September, the average daily maximum UV index is 4. A UV Index reading of 3 to 5 represents a medium vulnerability from exposure to the Sun's UV rays for the average person.Note: The maximum daily UV index of 4 during September translates into the following directions:
Be mindful. Individuals with a lighter skin tone may suffer burns in less than 30 minutes. Direct Sun exposure should be minimized especially during midday when radiation is most intense. Sun-related eye harm can be minimized with proper sunglasses offering UVA and UVB coverage. 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
Spearfish, SD
- Average high temperature in September: 72.5°F
The warmest month (with the highest average high temperature) is July (83.8°F).
The month with the lowest average high temperature is December (30.9°F).
- Average low temperature in September: 52°F
The month with the highest average low temperature is July (61°F).
The coldest month (with the lowest average low temperature) is February (16.2°F).
Average pressure in September
Spearfish, SD
- Average pressure in September: 29.93"Hg
The month with the highest atmospheric pressure is January (30.14"Hg).
The month with the lowest atmospheric pressure is June (29.84"Hg).
Average wind speed in September
Spearfish, SD
- Average wind speed in September: 8.8mph
The windiest month (with the highest average wind speed) is January (10.2mph).
The calmest month (with the lowest average wind speed) is August (8mph).
Average humidity in September
Spearfish, SD
- Average humidity in September: 50%
The month with the highest relative humidity is January (79%).
The month with the lowest relative humidity is August (49%).
Average rainfall in September
Spearfish, SD
- Average rainfall in September: 0.79"
The wettest month (with the highest rainfall) is May (2.32").
The driest month (with the least rainfall) is January (0.59").
Average rainfall days in September
Spearfish, SD
- Average rainfall days in September: 7.6 days
The month with the highest number of rainy days is May (15.6 days).
The month with the least rainy days is February (2.9 days).
Average snowfall in September
Spearfish, SD
- Average snowfall in September: 0.16"
The month with the highest snowfall is April (7.36").
The months with the least snowfall are June, July and August (0").
Average snowfall days in September
Spearfish, SD
- Average snowfall days in September: 0.1 days
The month with the highest number of snowfall days is February (11.2 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in September /
Average sunshine in September
Spearfish, SD
- Average daylight in September: 12h and 30min
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: 10h and 36min
The month with the most sunshine is August (Average sunshine: 11h and 42min).
The month with the least sunshine is February (Average sunshine: 5h and 42min).
Average sunshine days in September
Spearfish, SD
- Average sunshine days in September: 20.1 days
The month with the most sunshine days is November (20.3 days).
The month with the least sunshine days is May (12.7 days).
Average UV index in September
Spearfish, SD
- Average UV index in September: 4
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, April, November and December (UV index 2).
Average cloud cover in September
Spearfish, SD
- Average cloud cover in September: 18
The month with the most cloud cover is February (Cloud cover 41).
The month with the least cloud cover is August (Cloud cover 16).
Average visibility in September
Spearfish, SD
- 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).
