December weather in Keystone, SD
The average temperature in Keystone in December is 28.2°F (19.8°F–36.6°F). Average precipitation: 0.50 inches. Average snowfall is 6.6 inches.
December is a winter month in Keystone, and is cooler than the annual average of 45.7°F. Daily temperatures swing about 16.8°F between overnight low and afternoon high. Expect about 5 days with precipitation. Daylight averages about 8h 44m. For travel, December is cold.
Avg High
36.6°F
Avg Low
19.8°F
Precipitation
0.50 in
Snow
6.6 in
December records in Keystone
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| December 1 | 62.1°F (2021) | -11.9°F (1985) | 0.63 in (2018) |
| December 2 | 66.0°F (1988) | -11.9°F (1985) | 0.22 in (1964) |
| December 3 | 61.0°F (1975) | -5.1°F (1972) | 0.37 in (1964) |
| December 4 | 64.9°F (1965) | -9.9°F (1972) | 0.31 in (1972) |
| December 5 | 57.0°F (1963) | -15.0°F (1972) | 0.38 in (1977) |
| December 6 | 57.9°F (1984) | -16.1°F (2013) | 0.20 in (2017) |
| December 7 | 63.0°F (1984) | -17.0°F (2013) | 0.15 in (1994) |
| December 8 | 63.0°F (2024) | -20.0°F (1972) | 0.15 in (2007) |
| December 9 | 62.1°F (2020) | -17.0°F (1972) | 0.20 in (2021) |
| December 10 | 61.0°F (1981) | -8.0°F (1977) | 0.62 in (2021) |
| December 11 | 64.0°F (1993) | -7.1°F (2000) | 0.24 in (1965) |
| December 12 | 68.0°F (2014) | -5.1°F (2000) | 0.30 in (2025) |
| December 13 | 62.1°F (2014) | -7.1°F (1963) | 0.28 in (2008) |
| December 14 | 66.9°F (1997) | -16.1°F (2008) | 0.36 in (1996) |
| December 15 | 57.0°F (2025) | -18.0°F (2008) | 0.25 in (2015) |
| December 16 | 57.9°F (1962) | -15.0°F (1964) | 0.53 in (2016) |
| December 17 | 64.0°F (1976) | -24.0°F (1964) | 0.17 in (1963) |
| December 18 | 64.9°F (1979) | -13.0°F (1983) | 0.57 in (1973) |
| December 19 | 59.0°F (1979) | -16.1°F (1990) | 0.40 in (1985) |
| December 20 | 60.1°F (2003) | -22.0°F (1990) | 0.22 in (1989) |
| December 21 | 59.0°F (1994) | -31.0°F (1983) | 0.58 in (1996) |
| December 22 | 60.1°F (2019) | -23.1°F (1989) | 0.34 in (1966) |
| December 23 | 60.1°F (1994) | -23.1°F (1983) | 0.21 in (1996) |
| December 24 | 60.1°F (2025) | -27.9°F (1983) | 0.24 in (1964) |
| December 25 | 61.0°F (2025) | -14.1°F (1983) | 0.65 in (2016) |
| December 26 | 55.0°F (1980) | -8.0°F (1996) | 0.62 in (2023) |
| December 27 | 64.9°F (1980) | -5.1°F (1988) | 0.18 in (1987) |
| December 28 | 62.1°F (1980) | -8.0°F (1992) | 0.24 in (2019) |
| December 29 | 54.0°F (1999) | -20.9°F (1990) | 0.20 in (2017) |
| December 30 | 57.0°F (1980) | -27.0°F (1990) | 0.28 in (2018) |
| December 31 | 54.0°F (1996) | -27.0°F (1990) | 0.39 in (2010) |