Weather on October 21
Boulder, CO
55 Years of Data
Avg High
66°F
Avg Low
37°F
Warmest
2003
66°F avg
Coldest
1984
28°F avg
About This Date
October 21st in Boulder, CO typically brings mild fall weather, with average highs around 66°F and lows near 37°F — a 29°F daily swing. Over 55 years of records, the warmest October 21st was in 2003 (66°F average), while the coldest was 1984 (28°F) — a 38°F range across recorded history. Precipitation has occurred on 24% of recorded October 21st dates, with snow falling 5% of the time (heaviest snowfall: 5.8"). The last decade has been 5.0°F warmer on this date compared to 20-30 years ago.
The last decade has been 5.0°F warmer on this date compared to 20-30 years ago.
Planning for October 21st in Boulder, CO? Great weather for outdoor activities.
Warming Trend
0.6°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 72° | 34° | 53° | — | — |
| 2024 | 68° | 50° | 59° | — | — |
| 2023 | 79° | 46° | 62° | — | — |
| 2022 | 77° | 50° | 64° | — | — |
| 2021 | 63° | 36° | 49° | — | — |
| 2020 | 64° | 36° | 50° | — | — |
| 2019 | 52° | 34° | 43° | — | — |
| 2018 | 73° | 39° | 56° | — | — |
| 2017 | 66° | 35° | 51° | — | — |
| 2016 | 76° | 37° | 56° | — | — |
| 2015 | 60° | 44° | 52° | 2.62" | — |
| 2014 | 73° | 44° | 59° | — | — |
| 2013 | 61° | 27° | 44° | 0.03" | — |
| 2012 | 72° | 51° | 61° | — | — |
| 2011 | 73° | 39° | 56° | — | — |
| 2010 | 73° | 38° | 55° | — | — |
| 2009 | 45° | 32° | 38° | 0.99" | 0.1" |
| 2008 | 66° | 46° | 56° | 0.15" | — |
| 2007 | 64° | 32° | 48° | 0.2" | 0.1" |
| 2006 | 49° | 29° | 39° | 1.7" | 5.8" |
| 2005 | 61° | 45° | 53° | 0.23" | — |
| 2004 | 68° | 38° | 53° | — | — |
| 2003warmest | 83° | 49° | 66° | — | — |
| 2002 | 59° | 31° | 45° | — | — |
| 2001 | 58° | 36° | 47° | — | — |
| 2000 | 72° | 34° | 53° | — | — |
| 1999 | 71° | 40° | 55° | — | — |
| 1998 | 58° | 28° | 43° | — | — |
| 1997 | 53° | 36° | 44° | 0.23" | — |
| 1996 | 45° | 24° | 34° | — | — |
| 1995 | 74° | 43° | 58° | — | — |
| 1994 | 66° | 39° | 53° | — | — |
| 1993 | 62° | 30° | 46° | — | — |
| 1992 | 79° | 45° | 62° | — | — |
| 1991 | 74° | 39° | 56° | — | — |
| 1990 | 56° | 24° | 40° | — | — |
| 1989 | 73° | 26° | 50° | — | — |
| 1988 | 71° | 35° | 53° | — | — |
| 1987 | 74° | 27° | 50° | — | — |
| 1986 | 48° | 40° | 44° | 0.51" | — |
| 1985 | 72° | 39° | 55° | — | — |
| 1984coldest | 30° | 27° | 28° | 0.51" | — |
| 1983 | 70° | 31° | 50° | — | — |
| 1982 | 62° | 33° | 48° | — | — |
| 1981 | 64° | 31° | 47° | 0.33" | — |
| 1980 | 69° | 36° | 52° | — | — |
| 1979 | 54° | 35° | 44° | 1.63" | — |
| 1978 | 68° | 41° | 55° | — | — |
| 1977 | 72° | 44° | 58° | — | — |
| 1976 | 61° | 25° | 43° | — | — |
| 1975 | 79° | 44° | 61° | — | — |
| 1974 | 75° | 46° | 61° | — | — |
| 1973 | 77° | 44° | 61° | — | — |
| 1972 | 62° | 36° | 49° | 1.12" | — |
| 1971 | 65° | 37° | 51° | — | — |
55 years of data from BOULDER MUNI AP