Weather on March 21
Boulder, CO
55 Years of Data
Avg High
59°F
Avg Low
30°F
Warmest
2026
70°F avg
Coldest
2006
19°F avg
About This Date
March 21st in Boulder, CO typically brings cool spring weather, with average highs around 59°F and lows near 30°F — a 29°F daily swing. Over 56 years of records, the warmest March 21st was in 2026 (70°F average), while the coldest was 2006 (19°F) — a 51°F range across recorded history. Precipitation has occurred on 13% of recorded March 21st dates, with snow falling 7% of the time (heaviest snowfall: 3"). The last decade has been 3.3°F warmer on this date compared to 20-30 years ago.
The last decade has been 3.3°F warmer on this date compared to 20-30 years ago.
Planning for March 21st in Boulder, CO? Bring layers as temperatures can vary throughout the day.
Warming Trend
1.4°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2026warmest | 90° | 50° | 70° | — | — |
| 2025 | 54° | 37° | 45° | — | — |
| 2024 | 64° | 34° | 49° | — | — |
| 2023 | 55° | 32° | 44° | — | — |
| 2022 | 50° | 32° | 41° | — | — |
| 2021 | 54° | 32° | 43° | 0.61" | — |
| 2020 | 46° | 21° | 34° | — | — |
| 2019 | 57° | 32° | 45° | — | — |
| 2018 | 59° | 30° | 45° | — | — |
| 2017 | 69° | 36° | 52° | — | — |
| 2016 | 72° | 33° | 52° | — | — |
| 2015 | 71° | 35° | 53° | — | — |
| 2014 | 58° | 28° | 43° | — | — |
| 2013 | 60° | 35° | 48° | — | — |
| 2012 | 65° | 26° | 45° | — | — |
| 2011 | 73° | 33° | 53° | — | — |
| 2010 | 59° | 19° | 39° | — | — |
| 2009 | 73° | 34° | 53° | — | — |
| 2008 | 55° | 34° | 44° | — | — |
| 2007 | 71° | 48° | 60° | — | — |
| 2006coldest | 26° | 12° | 19° | 0.08" | 1.2" |
| 2005 | 52° | 36° | 44° | — | — |
| 2004 | 60° | 27° | 43° | — | — |
| 2003 | 51° | 32° | 42° | 0.15" | — |
| 2002 | 54° | 12° | 33° | 0.05" | 1.8" |
| 2001 | 65° | 38° | 51° | — | — |
| 2000 | 38° | 25° | 31° | 0.51" | 3" |
| 1999 | 69° | 32° | 51° | — | — |
| 1998 | 56° | 27° | 41° | — | — |
| 1997 | 73° | 41° | 57° | — | — |
| 1996 | 55° | 39° | 47° | — | — |
| 1995 | 76° | 37° | 56° | — | — |
| 1994 | 66° | 28° | 47° | — | — |
| 1993 | 57° | 35° | 46° | — | — |
| 1992 | 51° | 28° | 40° | 0.3" | 0.8" |
| 1991 | 55° | 31° | 43° | — | — |
| 1990 | 72° | 36° | 54° | — | — |
| 1989 | 62° | 14° | 38° | — | — |
| 1988 | 73° | 43° | 58° | — | — |
| 1987 | 46° | 23° | 35° | — | — |
| 1986 | 70° | 31° | 50° | — | — |
| 1985 | 63° | 27° | 45° | — | — |
| 1984 | 61° | 28° | 44° | — | — |
| 1983 | 34° | 8° | 21° | — | — |
| 1982 | 48° | 22° | 35° | — | — |
| 1981 | 48° | 26° | 37° | — | — |
| 1980 | 59° | 21° | 40° | — | — |
| 1979 | 43° | 31° | 37° | — | — |
| 1978 | 72° | 33° | 52° | — | — |
| 1977 | 49° | 16° | 32° | — | — |
| 1976 | 46° | 29° | 37° | — | — |
| 1975 | 66° | 36° | 51° | 0.1" | — |
| 1974 | 51° | 10° | 31° | — | — |
| 1973 | 54° | 32° | 43° | — | — |
| 1972 | 67° | 29° | 48° | — | — |
| 1971 | 65° | 30° | 47° | — | — |
56 years of data from BOULDER MUNI AP