Keystone, SD weather in December
In December, Keystone sees highs around 37°F and lows around 13°F: cold and mostly dry, with some snow. Expect about 5 wet days. Snowfall averages about 5.4 in.
- Normal high
- 37°F
- Normal low
- 13°F
- Wet days
- 5
- 0.4 in total
- Snowfall
- 5.4 in
- snow on the ground 15 days
How December changes from start to finish
| December 1 | December 31 | |
|---|---|---|
| Normal high | 39°F | 36°F |
| Normal low | 16°F | 12°F |
| Chance of a wet day | 15% | 18% |
| Sunrise / sunset | 7:08 am / 4:17 pm | 7:27 am / 4:25 pm |
| Daylight | 9.2 h | 9.0 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Mountain Time).
A typical December day
- 6 am21°Fdew point 10°F
- 9 am26°Fdew point 12°F
- Noon32°Fdew point 12°F
- 3 pm32°Fdew point 12°F
- 6 pm25°Fdew point 12°F
- 9 pm23°Fdew point 11°F
NOAA hourly normals (local standard time) from Custer Co Airport (15 mi away); average wind 7 mph; clear or few clouds in 49% of daytime hours, mostly cloudy or overcast in 41%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F0 of 31
- Hot dayshigh 90°F or more0 of 31
- Muggy daysdaily mean dew point 65°F or more0 of 31
- Wet daysat least 0.01 in of rain or melted snow5 of 31
- Notable rainat least 0.10 in1 of 31
- Freezing nightslow 32°F or below31 of 31
- Snow on the groundsnow depth 1 in or more15 of 31
Average days per December, counted from daily records for each year 1991-2020.
Rain and snow in December
Normal precipitation is 0.4 in; a dry December brings about 0.1 in and a wet one about 0.5 in (25th and 75th percentiles). Days with half an inch or more are rare. Normal snowfall is 5.4 in, with about 2 days of an inch or more.
How December varies from year to year
- Warmest December, 1991-20201999: average high 43°F
- Coolest December2009: average high 26°F
- Wettest December2018: 1.0 in
- Driest December1991: 0.01 in
- Highest reading70°F (December 15, 1997)
- Lowest reading-23°F (December 21, 1998)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
December compared with November and January
| November | December | January | |
|---|---|---|---|
| Normal high | 45°F | 37°F | 36°F |
| Normal low | 20°F | 13°F | 11°F |
| Wet days | 5 | 5 | 6 |
| Comfortable days | 2 | 0 | 0 |
| Daylight | 9.7 h | 9.0 h | 9.3 h |
Highs change by -8°F from November and -1°F into January.
Nearby alternatives in December
- Warmer: Fort Collins, CO244 mi · high 44°F · 4 wet days
- Cooler: Medora, ND209 mi · high 31°F · 6 wet days
How Keystone ranks in December
- Normal high321st warmest of 378 cities; 2nd of 4 in South Dakota
- Wet days47th driest of 378
- Comfortable days284th most of 340
What to pack for Keystone in December
- A warm jacket – lows near 13°F, highs near 37°F
- Waterproof boots – snow on the ground on about 15 days
- A hat and gloves – about 31 freezing nights
Heating and cooling
December has 1249 heating degree days and 0 cooling degree days (base 65°F), 14% of the year's total heating and cooling demand.
Questions
How cold is Keystone in December?
The normal high is 37°F and the normal low is 13°F. From 1991 to 2020 the coldest December reading was -23°F (December 21, 1998).
Does it rain a lot in Keystone in December?
About 5 days in December have at least 0.01 in of precipitation, and the normal total is 0.4 in. The wettest December in 1991-2020 was in 2018 (1.0 in); the driest was in 1991 (0.01 in).
Does it snow in Keystone in December?
Yes. Normal snowfall in December is 5.4 in, and snow covers the ground on about 15 days.
Is December a good time to visit Keystone?
December ranks 12th of 12 months on our comfort score for Keystone (33 out of 100). It has almost no comfortable days. The best month is June.
Where the numbers come from
- Temperature, rain, snowfall, snow depth and frost dates: Pactola Dam (USC00396427), 12 mi NNW of the city center, 4,720 ft (385 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour: Custer Co Airport (USW00094032), 15 mi SW of the city center, 5,545 ft (1,210 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Cloud cover: Ellsworth AFB (USW00024006), 24 mi NE of the city center, 3,215 ft (1,120 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Rapid City Regional Airport (726620-24090), 21 mi ENE of the city center, 3,162 ft (1,173 ft lower than the city). Hourly observations, 1991-2020.