Weather on September 15
Longmont, CO
55 Years of Data
Avg High
78°F
Avg Low
46°F
Warmest
2015
71°F avg
Coldest
1988
47°F avg
About This Date
September 15th in Longmont, CO typically brings pleasant fall weather, with average highs around 78°F and lows near 46°F — a 32°F daily swing. Over 55 years of records, the warmest September 15th was in 2015 (71°F average), while the coldest was 1988 (47°F) — a 24°F range across recorded history. Rain or other precipitation has occurred on about 25% of September 15th dates historically, with the wettest September 15th recording 4.93" of rain. The last decade has been 5.4°F warmer on this date compared to 20-30 years ago.
The last decade has been 5.4°F warmer on this date compared to 20-30 years ago.
Planning for September 15th in Longmont, CO? Great weather for outdoor activities.
Warming Trend
1.4°F per decade on this date
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 74° | 50° | 62° | 0.03" | — |
| 2024 | 87° | 51° | 69° | — | — |
| 2023 | 72° | 52° | 62° | 0.61" | — |
| 2022 | 79° | 53° | 66° | 0.05" | — |
| 2021 | 75° | 50° | 63° | — | — |
| 2020 | 86° | 46° | 66° | — | — |
| 2019 | 88° | 49° | 68° | — | — |
| 2018 | 92° | 51° | 71° | — | — |
| 2017 | 90° | 52° | 71° | — | — |
| 2016 | 74° | 44° | 59° | 0.05" | — |
| 2015warmest | 86° | 56° | 71° | — | — |
| 2014 | 77° | 46° | 62° | — | — |
| 2013 | 71° | 55° | 63° | 4.93" | — |
| 2012 | 86° | 46° | 66° | — | — |
| 2011 | 56° | 48° | 52° | 3.56" | — |
| 2010 | 87° | 52° | 69° | — | — |
| 2009 | 83° | 53° | 68° | — | — |
| 2008 | 72° | 40° | 56° | — | — |
| 2007 | 89° | 47° | 68° | — | — |
| 2006 | 80° | 59° | 70° | 0.08" | — |
| 2005 | 76° | 42° | 59° | — | — |
| 2004 | 81° | 42° | 61° | — | — |
| 2003 | 70° | 36° | 53° | — | — |
| 2002 | 78° | 41° | 60° | — | — |
| 2001 | 81° | 49° | 65° | 0.33" | — |
| 2000 | 86° | 44° | 65° | — | — |
| 1999 | 70° | 35° | 52° | — | — |
| 1998 | 80° | 45° | 62° | — | — |
| 1997 | 88° | 46° | 67° | — | — |
| 1996 | 69° | 49° | 59° | 0.28" | — |
| 1995 | 81° | 41° | 61° | — | — |
| 1994 | 81° | 46° | 63° | — | — |
| 1993 | 67° | 28° | 47° | — | — |
| 1992 | 88° | — | — | — | — |
| 1991 | 82° | 45° | 63° | — | — |
| 1990 | 90° | 44° | 67° | — | — |
| 1989 | 72° | 34° | 53° | — | — |
| 1988coldest | 58° | 36° | 47° | 0.64" | — |
| 1987 | 80° | 48° | 64° | 1.24" | — |
| 1986 | 85° | 44° | 64° | — | — |
| 1985 | 80° | 55° | 68° | 0.08" | — |
| 1984 | 56° | 43° | 49° | — | — |
| 1983 | 74° | 49° | 61° | — | — |
| 1982 | 61° | 47° | 54° | 0.81" | — |
| 1981 | 87° | 49° | 68° | — | — |
| 1980 | 82° | 49° | 65° | — | — |
| 1979 | 67° | 36° | 51° | — | — |
| 1978 | 80° | 48° | 64° | — | — |
| 1977 | 83° | 48° | 65° | — | — |
| 1976 | 76° | 46° | 61° | 0.28" | — |
| 1975 | 79° | 45° | 62° | — | — |
| 1974 | 72° | 37° | 54° | — | — |
| 1973 | 82° | 40° | 61° | — | — |
| 1972 | 82° | 45° | 63° | — | — |
| 1971 | 68° | 37° | 53° | — | — |
55 years of data from LONGMONT 2 ESE