Weather on May 21
Longmont, CO
55 Years of Data
About This Date
May 21st in Longmont, CO typically brings pleasant spring weather, with average highs around 72°F and lows near 44°F — a 28°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 35% of recorded May 21st dates, with snow falling 4% of the time (heaviest snowfall: 1.9"). The last decade has been 6.3°F cooler on this date compared to 20-30 years ago.
The last decade has been 6.3°F cooler on this date compared to 20-30 years ago.
Planning for May 21st in Longmont, CO? Great weather for outdoor activities. Consider bringing rain gear or an umbrella.
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2026 | 58° | 40° | 49° | 0.18" | — |
| 2025 | 71° | 45° | 58° | — | — |
| 2024 | 69° | 43° | 56° | 0.25" | — |
| 2023 | 70° | 45° | 57° | — | — |
| 2022 | 40° | 34° | 37° | 2.13" | 1.7" |
| 2021 | 78° | 49° | 63° | — | — |
| 2020 | 90° | 44° | 67° | — | — |
| 2019coldest | 42° | 32° | 37° | 2.01" | 1.9" |
| 2018 | 58° | 41° | 49° | 0.05" | — |
| 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° | — | — |
| 2008 | 81° | 53° | 67° | — | — |
| 2007 | 78° | 47° | 62° | 0.03" | — |
| 2006 | 90° | 52° | 71° | — | — |
| 2005warmest | 88° | 66° | 77° | — | — |
| 2004 | 74° | 54° | 64° | — | — |
| 2003 | 64° | 40° | 52° | — | — |
| 2002 | 66° | 40° | 53° | — | — |
| 2001 | 76° | 25° | 50° | 0.25" | — |
| 2000 | 69° | 40° | 54° | — | — |
| 1999 | 72° | 43° | 57° | 0.05" | — |
| 1998 | 87° | 49° | 68° | — | — |
| 1997 | 84° | 41° | 63° | — | — |
| 1996 | 73° | 42° | 58° | — | — |
| 1995 | 64° | 40° | 52° | 0.1" | — |
| 1994 | 85° | 40° | 62° | — | — |
| 1993 | 77° | 47° | 62° | 0.05" | — |
| 1992 | 88° | 50° | 69° | — | — |
| 1991 | 76° | 52° | 64° | 0.1" | — |
| 1990 | 82° | 43° | 62° | — | — |
| 1989 | 80° | 46° | 63° | — | — |
| 1988 | 55° | 38° | 46° | 0.08" | — |
| 1987 | 66° | 42° | 54° | 0.15" | — |
| 1986 | 85° | 47° | 66° | — | — |
| 1985 | 66° | 43° | 54° | — | — |
| 1984 | 89° | 50° | 70° | — | — |
| 1983 | 58° | 35° | 46° | 0.03" | — |
| 1982 | 70° | 41° | 55° | — | — |
| 1981 | 67° | 44° | 55° | — | — |
| 1980 | 78° | 47° | 62° | — | — |
| 1979 | 49° | 45° | 47° | 0.23" | — |
| 1978 | 72° | 48° | 60° | — | — |
| 1977 | 61° | 37° | 49° | 0.43" | — |
| 1976 | 76° | 52° | 64° | — | — |
| 1975 | 51° | 39° | 45° | 0.08" | — |
| 1974 | 65° | 42° | 53° | — | — |
| 1973 | 84° | 52° | 68° | — | — |
| 1972 | 85° | 46° | 65° | — | — |
| 1971 | 73° | 43° | 58° | — | — |
Longmont, CO Temperature Range by Month
Average monthly highs and lows. The shaded band shows the typical daily temperature range.
Longmont, CO Monthly Precipitation
Average rainfall and snowfall per month, in inches.
Longmont, CO Daily Temperature Calendar
Average daily high temperature for every day of the year. Each cell is the climatological mean for that calendar day across 55 years of NOAA data.
Best Time to Visit Longmont, CO
Longmont, CO has no months that meet our "pleasant" threshold — every season has tradeoffs.