Contents
- Weather in December
- Frequently asked questions
- Average temperature in December
- Average pressure in December
- Average wind speed in December
- Average humidity in December
- Average rainfall in December
- Average rainfall days in December
- Average snowfall in December
- Average snowfall days in December
- Average daylight in December
- Average sunshine in December
- Average sunshine days in December
- Average UV index in December
- Average cloud cover in December
- Average visibility in December
Weather in December
Temperature
Keystone's coldest temperatures are experienced in December, with average high temperatures of 29.8°F (-1.2°C) and lows of 16.5°F (-8.6°C).Humidity
In Keystone, the average relative humidity in December is 74%.Rainfall
In Keystone, in December, it is raining for 6.3 days, with typically 0.67" (17mm) of accumulated precipitation. In Keystone, during the entire year, the rain falls for 135.4 days and collects up to 20.39" (518mm) of precipitation.Snowfall
Months with snowfall are January through May, September through December. In Keystone, South Dakota, in December, during 11.5 snowfall days, 4.57" (116mm) of snow is typically accumulated. Throughout the year, there are 75.1 snowfall days, and 40.24" (1022mm) of snow is accumulated.Daylight
December has the shortest days of the year, with an average of 9h and 0min of daylight.On the first day of the month, sunrise is at 7:08 am and sunset at 4:17 pm. On the last day of December, sunrise is at 7:27 am and sunset at 4:26 pm MST.
Sunshine
In Keystone, the average sunshine in December is 6.2h.UV index
January through March, October through December, with an average maximum UV index of 2, are months with the lowest UV index. A UV Index estimate of 2, and below, represents a low threat to health from unsafe exposure to UV radiation for average individuals.Note: The daily maximum UV index of 2 in December interprets into the following advice:
Babies, children, and those with sensitive skin should always avoid extended periods in the sun. The Sun is most powerful around mid-day, so it's a good practice to reduce direct exposure. To best shield against UV radiation, choose sun-safe garments and dependable sunglasses. Note this! The Sun's UV radiation can nearly be doubled by the reflection off snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
What is the coldest time of year?
How cold is it in December?
What is the average humidity in December?
How much does it rain in December?
How many days does it snow in December in Keystone?
What is the month with the shortest days?
How many hours of daylight does Keystone have in December?
When is the sunrise / sunset in December?
How long on average sun shines in December?
What is the month with the lowest UV index?
What is the UV index intensity in December?
Average temperature in December
Keystone, SD
- Average high temperature in December: 29.8°F
The warmest month (with the highest average high temperature) is July (81.7°F).
The month with the lowest average high temperature is December (29.8°F).
- Average low temperature in December: 16.5°F
The month with the highest average low temperature is July (60.4°F).
The coldest month (with the lowest average low temperature) is February (16.2°F).
Average pressure in December
Keystone, SD
- Average pressure in December: 30.12"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The month with the lowest atmospheric pressure is June (29.84"Hg).
Average wind speed in December
Keystone, SD
- Average wind speed in December: 8.9mph
The windiest month (with the highest average wind speed) is April (9.5mph).
The calmest month (with the lowest average wind speed) is August (7mph).
Average humidity in December
Keystone, SD
- Average humidity in December: 74%
The months with the highest relative humidity are January and February (77%).
The months with the lowest relative humidity are August and September (52%).
Average rainfall in December
Keystone, SD
- Average rainfall in December: 0.67"
The wettest month (with the highest rainfall) is June (3.19").
The driest month (with the least rainfall) is January (0.47").
Average rainfall days in December
Keystone, SD
- Average rainfall days in December: 6.3 days
The month with the highest number of rainy days is May (18.6 days).
The month with the least rainy days is November (4.5 days).
Average snowfall in December
Keystone, SD
- Average snowfall in December: 4.57"
The month with the highest snowfall is April (7.24").
The months with the least snowfall are June, July and August (0").
Average snowfall days in December
Keystone, SD
- Average snowfall days in December: 11.5 days
The month with the highest number of snowfall days is February (12.9 days).
The months with the least snowfall days are June, July and August (0 days).
Average daylight in December /
Average sunshine in December
Keystone, SD
- Average daylight in December: 9h and 0min
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 December: 6h and 1min
The month with the most sunshine is August (Average sunshine: 11h and 42min).
The month with the least sunshine is February (Average sunshine: 6h and 0min).
Average sunshine days in December
Keystone, SD
- Average sunshine days in December: 18.1 days
The month with the most sunshine days is November (19.2 days).
The month with the least sunshine days is May (7.8 days).
Average UV index in December
Keystone, SD
- Average UV index in December: 2
The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, March, October, November and December (UV index 2).
Average cloud cover in December
Keystone, SD
- Average cloud cover in December: 34
The month with the most cloud cover is April (Cloud cover 38).
The month with the least cloud cover is August (Cloud cover 17).
Average visibility in December
Keystone, SD
- Average visibility in December: 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).
Keystone, South Dakota, USA
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