Weather on May 21
Boulder, CO
55 Years of Data
Avg High
72°F
Avg Low
45°F
Warmest
2005
77°F avg
Coldest
2019
37°F avg
About This Date
May 21st in Boulder, CO typically brings pleasant spring weather, with average highs around 72°F and lows near 45°F — a 27°F daily swing. Over 55 years of records, the warmest May 21st was in 2005 (77°F average), while the coldest was 2019 (37°F) — a 40°F range across recorded history. Precipitation has occurred on 25% of recorded May 21st dates, with snow falling 2% of the time (heaviest snowfall: 3.6"). The last decade has been 7.0°F cooler on this date compared to 20-30 years ago.
The last decade has been 7.0°F cooler on this date compared to 20-30 years ago.
Planning for May 21st in Boulder, CO? Great weather for outdoor activities.
Cooling Trend
0.4°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 77° | 41° | 59° | — | — |
| 2024 | 61° | 45° | 53° | — | — |
| 2023 | 75° | 52° | 63° | — | — |
| 2022 | 46° | 32° | 39° | — | — |
| 2021 | 73° | 52° | 62° | — | — |
| 2020 | 75° | 46° | 61° | — | — |
| 2019coldest | 41° | 32° | 37° | — | — |
| 2018 | 75° | 41° | 58° | — | — |
| 2017 | 67° | 35° | 51° | — | — |
| 2016 | 79° | 45° | 62° | — | — |
| 2015 | 50° | 39° | 45° | 0.18" | — |
| 2014 | 72° | 48° | 60° | 0.3" | — |
| 2013 | 68° | 38° | 53° | — | — |
| 2012 | 84° | 43° | 63° | — | — |
| 2011 | 66° | 38° | 52° | — | — |
| 2010 | 74° | 45° | 59° | — | — |
| 2009 | 52° | 48° | 50° | — | — |
| 2008 | 81° | 53° | 67° | — | — |
| 2007 | 78° | 47° | 62° | 0.03" | — |
| 2006 | 90° | 52° | 71° | — | — |
| 2005warmest | 88° | 66° | 77° | — | — |
| 2004 | 80° | 51° | 66° | — | — |
| 2003 | 77° | 38° | 57° | — | — |
| 2002 | 85° | 46° | 65° | 0.05" | — |
| 2001 | 56° | 26° | 41° | 0.84" | 3.6" |
| 2000 | 79° | 43° | 61° | — | — |
| 1999 | 79° | 46° | 62° | 0.1" | — |
| 1998 | 80° | 51° | 66° | — | — |
| 1997 | 75° | 48° | 62° | — | — |
| 1996 | 73° | 42° | 58° | — | — |
| 1995 | 76° | 40° | 58° | — | — |
| 1994 | 79° | 43° | 61° | — | — |
| 1993 | 75° | 50° | 63° | 0.25" | — |
| 1992 | 77° | 51° | 64° | 0.03" | — |
| 1991 | 79° | 53° | 66° | — | — |
| 1990 | 79° | 41° | 60° | — | — |
| 1989 | 74° | 49° | 61° | — | — |
| 1988 | 62° | 39° | 51° | 0.1" | — |
| 1987 | 54° | 43° | 48° | 0.79" | — |
| 1986 | 85° | 48° | 66° | — | — |
| 1985 | 65° | 42° | 53° | — | — |
| 1984 | 78° | 52° | 65° | — | — |
| 1983 | 75° | 37° | 56° | — | — |
| 1982 | 70° | 40° | 55° | — | — |
| 1981 | 66° | 45° | 55° | — | — |
| 1980 | 83° | 48° | 65° | — | — |
| 1979 | 49° | 45° | 47° | 0.23" | — |
| 1978 | 69° | 48° | 59° | — | — |
| 1977 | 66° | 33° | 50° | 0.15" | — |
| 1976 | 70° | 49° | 59° | 0.13" | — |
| 1975 | 46° | 38° | 42° | 0.94" | — |
| 1974 | 68° | 44° | 56° | — | — |
| 1973 | 77° | 58° | 67° | — | — |
| 1972 | 81° | 50° | 65° | — | — |
| 1971 | 74° | 42° | 58° | — | — |
55 years of data from BOULDER MUNI AP