Weather on September 21 at Yellowstone
Yellowstone National Park
Based on 55 years of data from Jackson, WY
Elevation Note: Yellowstone sits at 7,350 ft. Expect temperatures 26°F cooler than the data shown below, which comes from Jackson, WY at a lower elevation.
Planning Your Visit
September 21st in Yellowstone National Park (via Jackson, WY) typically brings mild fall weather, with average highs around 66°F and lows near 31°F — a 35°F daily swing. Over 55 years of records, the warmest September 21st was in 1991 (60°F average), while the coldest was 1995 (30°F) — a 30°F range across recorded history. Rain or other precipitation has occurred on about 22% of September 21st dates historically, with the wettest September 21st recording 2.31" of rain. The last decade has been 4.4°F cooler on this date compared to 20-30 years ago.
The last decade has been 4.4°F cooler on this date compared to 20-30 years ago.
Planning for September 21st in Yellowstone? Great weather for outdoor activities.
Year by Year History
| Year | High | Low | Precip | Snow |
|---|---|---|---|---|
| 2025 | 74°F | 30°F | 0" | 0" |
| 2024 | 67°F | 29°F | 0" | 0" |
| 2023 | 64°F | 40°F | 2.31" | 0" |
| 2022 | 75°F | 33°F | 0" | 0" |
| 2021 | 49°F | 21°F | 0" | 0" |
| 2020 | 61°F | 24°F | 0" | 0" |
| 2019 | 46°F | 38°F | 0.58" | 0" |
| 2018 | 60°F | 20°F | 0" | 0" |
| 2017 | 53°F | 32°F | 1.73" | 0" |
| 2016 | 76°F | 34°F | 0" | 0" |
| 2015 | 67°F | 29°F | 0" | 0" |
| 2014 | 73°F | 35°F | 0" | 0" |
| 2013 | 69°F | 26°F | 0.03" | 0" |
| 2012 | 71°F | 42°F | 0" | -- |
| 2011 | 71°F | 24°F | 0" | 0" |
| 2010 | 70°F | 20°F | 0" | 0" |
| 2009 | 65°F | 29°F | 0" | 0" |
| 2008 | 64°F | 39°F | 0" | 0" |
| 2007 | 71°F | 43°F | 0" | 0" |
| 2006 | 60°F | 38°F | -- | -- |
| 2005 | 75°F | 45°F | -- | -- |
| 2004 | 53°F | 28°F | -- | -- |
| 2003 | 67°F | 23°F | -- | -- |
| 2002 | 70°F | 38°F | -- | -- |
| 2001 | 77°F | 25°F | -- | -- |
| 2000 | 59°F | 45°F | 0" | -- |
| 1999 | 74°F | 25°F | -- | -- |
| 1998 | 62°F | 38°F | -- | -- |
| 1997 | 58°F | 44°F | 0" | 0" |
| 1996 | 63°F | 46°F | 0" | 0" |
| 1995 | 45°F | 15°F | 0" | -- |
| 1994 | 75°F | 26°F | 0" | 0" |
| 1993 | 68°F | 36°F | 0" | 0" |
| 1992 | 81°F | 27°F | 0" | 0" |
| 1991 | 76°F | 45°F | 0" | 0" |
| 1990 | 69°F | 30°F | 0" | 0" |
| 1989 | 71°F | 36°F | 0.36" | 0" |
| 1988 | 63°F | 34°F | 0.56" | 0" |
| 1987 | 78°F | 23°F | 0" | 0" |
| 1986 | 56°F | 24°F | 0.1" | -- |
| 1985 | 60°F | 28°F | 0.13" | 0" |
| 1984 | 72°F | 34°F | 1.07" | 0" |
| 1983 | 64°F | 12°F | 0" | 0" |
| 1982 | 71°F | 30°F | 0" | 0" |
| 1981 | 72°F | 28°F | 0" | 0" |
| 1980 | 58°F | 38°F | 0.71" | 0" |
| 1979 | 77°F | 26°F | 0" | 0" |
| 1978 | 54°F | 17°F | 0" | 0" |
| 1977 | 57°F | 37°F | 0.15" | 0" |
| 1976 | 73°F | 30°F | 0" | 0" |
| 1975 | 67°F | 16°F | 0" | 0" |
| 1974 | 75°F | 24°F | 0" | 0" |
| 1973 | 58°F | 40°F | 0" | 0" |
| 1972 | 67°F | 19°F | 0" | 0" |
| 1971 | 56°F | 21°F | 0.64" | 0" |