May weather in Keystone, SD
The average temperature in Keystone in May is 50.6°F (41.5°F–59.6°F). Average precipitation: 4.80 inches. Average snowfall is 1.5 inches.
May is a spring month in Keystone, and is warmer than the annual average of 45.7°F. Daily temperatures swing about 18.1°F between overnight low and afternoon high. Expect about 14 days with precipitation. Daylight averages about 14h 33m. For travel, May is a comfortable month to visit.
Avg High
59.6°F
Avg Low
41.5°F
Precipitation
4.80 in
Snow
1.5 in
May records in Keystone
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| May 1 | 79.0°F (1987) | 14.0°F (1967) | 0.74 in (1978) |
| May 2 | 80.1°F (1985) | 19.9°F (2005) | 1.42 in (1964) |
| May 3 | 84.0°F (1986) | 19.0°F (1967) | 0.40 in (1991) |
| May 4 | 82.9°F (1966) | 21.0°F (1967) | 1.47 in (1978) |
| May 5 | 84.0°F (2000) | 23.0°F (1976) | 2.00 in (1993) |
| May 6 | 80.1°F (1992) | 28.0°F (2010) | 1.45 in (2015) |
| May 7 | 82.0°F (1966) | 23.0°F (1984) | 1.43 in (1983) |
| May 8 | 84.0°F (1985) | 25.0°F (1979) | 3.38 in (1995) |
| May 9 | 82.0°F (1962) | 15.1°F (2010) | 1.75 in (1971) |
| May 10 | 81.0°F (2012) | 21.0°F (1979) | 1.67 in (2010) |
| May 11 | 84.9°F (2025) | 21.9°F (1967) | 1.71 in (1998) |
| May 12 | 84.9°F (2025) | 24.1°F (1980) | 1.29 in (2005) |
| May 13 | 86.0°F (2001) | 18.0°F (1980) | 1.07 in (1994) |
| May 14 | 88.0°F (1976) | 26.1°F (2016) | 2.71 in (1965) |
| May 15 | 90.0°F (1978) | 30.0°F (2023) | 1.54 in (2015) |
| May 16 | 84.0°F (1978) | 28.9°F (2009) | 0.88 in (1981) |
| May 17 | 84.0°F (1972) | 30.0°F (2010) | 1.97 in (1981) |
| May 18 | 86.0°F (1992) | 28.0°F (2019) | 1.35 in (1962) |
| May 19 | 89.1°F (1992) | 28.0°F (1971) | 2.31 in (2011) |
| May 20 | 84.0°F (1964) | 24.1°F (1963) | 3.05 in (2016) |
| May 21 | 84.9°F (1964) | 26.1°F (1963) | 2.52 in (1962) |
| May 22 | 84.9°F (1980) | 28.9°F (1963) | 1.43 in (1971) |
| May 23 | 91.0°F (1967) | 27.0°F (2002) | 1.90 in (1996) |
| May 24 | 82.0°F (1967) | 25.0°F (2002) | 2.46 in (2015) |
| May 25 | 82.9°F (1985) | 30.0°F (1981) | 3.20 in (1997) |
| May 26 | 87.1°F (1969) | 28.9°F (1984) | 1.30 in (1967) |
| May 27 | 93.0°F (1969) | 25.0°F (1963) | 2.40 in (1970) |
| May 28 | 91.9°F (1969) | 30.0°F (1984) | 1.75 in (2019) |
| May 29 | 89.1°F (2003) | 24.1°F (1984) | 2.22 in (2011) |
| May 30 | 84.9°F (1984) | 25.0°F (1981) | 1.54 in (1971) |
| May 31 | 84.0°F (1984) | 27.0°F (1982) | 1.06 in (1967) |