Weather on September 21
Sioux Falls, SD
55 Years of Data
About This Date
September 21st in Sioux Falls, SD typically brings pleasant fall weather, with average highs around 71°F and lows near 46°F — a 25°F daily swing. Over 55 years of records, the warmest September 21st was in 2005 (77°F average), while the coldest was 1995 (39°F) — a 38°F range across recorded history. Rain or other precipitation has occurred on about 33% of September 21st dates historically, with the wettest September 21st recording 3.35" of rain. The last decade has been 9.7°F warmer on this date compared to 20-30 years ago.
The last decade has been 9.7°F warmer on this date compared to 20-30 years ago.
Planning for September 21st in Sioux Falls, SD? Great weather for outdoor activities. Consider bringing rain gear or an umbrella.
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 83° | 51° | 67° | — | — |
| 2024 | 80° | 55° | 68° | — | — |
| 2023 | 73° | 60° | 67° | 0.46" | — |
| 2022 | 71° | 49° | 60° | — | — |
| 2021 | 69° | 45° | 57° | — | — |
| 2020 | 84° | 61° | 72° | — | — |
| 2019 | 82° | 57° | 70° | 0.05" | — |
| 2018 | 59° | 45° | 52° | — | — |
| 2017 | 86° | 49° | 67° | — | — |
| 2016 | 88° | 63° | 75° | — | — |
| 2015 | 81° | 58° | 69° | — | — |
| 2014 | 72° | 47° | 59° | — | — |
| 2013 | 75° | 35° | 55° | — | — |
| 2012 | 71° | 45° | 58° | — | — |
| 2011 | 61° | 40° | 50° | — | — |
| 2010 | 72° | 51° | 61° | 0.41" | — |
| 2009 | 67° | 52° | 59° | 0.53" | — |
| 2008 | 81° | 60° | 70° | — | — |
| 2007 | 77° | 46° | 62° | 0.38" | — |
| 2006 | 57° | 50° | 54° | 3.35" | — |
| 2005warmest | 92° | 62° | 77° | — | — |
| 2004 | 64° | 56° | 60° | 0.41" | — |
| 2003 | 71° | 50° | 61° | 0.76" | — |
| 2002 | 64° | 44° | 54° | — | — |
| 2001 | 73° | 47° | 60° | — | — |
| 2000 | 61° | 29° | 45° | 0.13" | — |
| 1999 | 68° | 29° | 48° | — | — |
| 1998 | 56° | 42° | 49° | 0.03" | — |
| 1997 | 62° | 32° | 47° | 0.03" | — |
| 1996 | 67° | 48° | 57° | — | — |
| 1995coldest | 46° | 32° | 39° | — | — |
| 1994 | 78° | 47° | 62° | 0.38" | — |
| 1993 | 73° | 51° | 62° | — | — |
| 1992 | 78° | 45° | 61° | — | — |
| 1991 | 72° | 47° | 59° | — | — |
| 1990 | 72° | 47° | 59° | — | — |
| 1989 | 73° | 53° | 63° | — | — |
| 1988 | 78° | 47° | 62° | — | — |
| 1987 | 67° | 46° | 56° | — | — |
| 1986 | 80° | 60° | 70° | 0.97" | — |
| 1985 | 55° | 38° | 46° | 0.3" | — |
| 1984 | 85° | 55° | 70° | — | — |
| 1983 | 55° | 29° | 42° | — | — |
| 1982 | 64° | 33° | 49° | — | — |
| 1981 | 75° | 51° | 63° | — | — |
| 1980 | 75° | 44° | 60° | 0.38" | — |
| 1979 | 66° | 37° | 52° | — | — |
| 1978 | 68° | 36° | 52° | — | — |
| 1977 | 68° | 55° | 62° | 0.48" | — |
| 1976 | 72° | 41° | 56° | — | — |
| 1975 | 61° | 37° | 49° | — | — |
| 1974 | 61° | 32° | 46° | — | — |
| 1973 | 70° | 50° | 60° | 0.25" | — |
| 1972 | 65° | 36° | 50° | — | — |
| 1971 | 54° | 45° | 49° | 0.53" | — |