Weather on September 20
Longmont, CO
55 Years of Data
About This Date
September 20th in Longmont, CO typically brings pleasant fall weather, with average highs around 77°F and lows near 44°F — a 33°F daily swing. Over 55 years of records, the warmest September 20th was in 1980 (71°F average), while the coldest was 1971 (39°F) — a 32°F range across recorded history. Rain or other precipitation has occurred on about 22% of September 20th dates historically, with the wettest September 20th recording 1.24" of rain. The last decade has been 9.5°F warmer on this date compared to 20-30 years ago.
The last decade has been 9.5°F warmer on this date compared to 20-30 years ago.
Planning for September 20th in Longmont, CO? Great weather for outdoor activities.
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 79° | 46° | 62° | — | — |
| 2024 | 83° | 48° | 65° | — | — |
| 2023 | 77° | 47° | 62° | — | — |
| 2022 | 90° | 51° | 70° | — | — |
| 2021 | 85° | 50° | 67° | — | — |
| 2020 | 88° | 54° | 71° | — | — |
| 2019 | 84° | 49° | 66° | — | — |
| 2018 | 82° | 53° | 68° | 0.13" | — |
| 2017 | 87° | 43° | 65° | — | — |
| 2016 | 85° | 55° | 70° | — | — |
| 2015 | 85° | 47° | 66° | — | — |
| 2014 | 78° | 53° | 66° | — | — |
| 2013 | 71° | 43° | 57° | — | — |
| 2012 | 81° | 48° | 64° | — | — |
| 2011 | 76° | 44° | 60° | — | — |
| 2010 | 90° | 53° | 71° | — | — |
| 2009 | 81° | 50° | 65° | — | — |
| 2008 | 77° | 47° | 62° | — | — |
| 2007 | 88° | 47° | 67° | — | — |
| 2006 | 76° | 41° | 58° | — | — |
| 2005 | 88° | 48° | 68° | — | — |
| 2004 | 92° | 49° | 70° | — | — |
| 2003 | 72° | 41° | 56° | — | — |
| 2002 | 72° | 35° | 53° | — | — |
| 2001 | 76° | 39° | 57° | — | — |
| 2000 | 79° | 38° | 58° | 1.24" | — |
| 1999 | 50° | 37° | 44° | 0.74" | — |
| 1998 | 87° | 45° | 66° | 0.03" | — |
| 1997 | 59° | 41° | 50° | 0.99" | — |
| 1996 | 64° | 33° | 49° | — | — |
| 1995 | 54° | 44° | 49° | 0.13" | — |
| 1994 | 79° | 48° | 63° | — | — |
| 1993 | 73° | 35° | 54° | — | — |
| 1992 | 77° | — | — | — | — |
| 1991 | 68° | 36° | 52° | — | — |
| 1990 | 75° | 43° | 59° | — | — |
| 1989 | 80° | 50° | 65° | — | — |
| 1988 | 74° | 30° | 52° | — | — |
| 1987 | 73° | 33° | 53° | — | — |
| 1986 | 72° | 46° | 59° | — | — |
| 1985 | 57° | 44° | 51° | 0.03" | — |
| 1984 | 92° | 46° | 69° | — | — |
| 1983 | 89° | 29° | 59° | 0.28" | — |
| 1982 | 70° | 48° | 59° | 0.03" | — |
| 1981 | 85° | 49° | 67° | — | — |
| 1980warmest | 92° | 50° | 71° | 0.89" | — |
| 1979 | 86° | 48° | 67° | — | — |
| 1978 | 55° | 36° | 45° | 0.23" | — |
| 1977 | 79° | 45° | 62° | — | — |
| 1976 | 59° | 50° | 55° | 0.51" | — |
| 1975 | 65° | 32° | 48° | — | — |
| 1974 | 68° | 41° | 55° | — | — |
| 1973 | 85° | 44° | 64° | — | — |
| 1972 | 84° | 48° | 66° | — | — |
| 1971coldest | 55° | 23° | 39° | — | — |
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.