Weather on September 11
Longmont, CO
55 Years of Data
About This Date
September 11th in Longmont, CO typically brings warm fall weather, with average highs around 81°F and lows near 49°F — a 32°F daily swing. Over 55 years of records, the warmest September 11th was in 1994 (75°F average), while the coldest was 2020 (45°F) — a 30°F range across recorded history. Rain or other precipitation has occurred on about 33% of September 11th dates historically, with the wettest September 11th recording 4.88" of rain. Temperatures on this date have remained relatively stable over the past several decades.
Temperatures on this date have remained relatively stable over the past several decades.
Planning for September 11th in Longmont, CO? Stay hydrated and seek shade during peak afternoon hours. Consider bringing rain gear or an umbrella.
| Year | High | Low | Avg | Precip | Snow |
|---|---|---|---|---|---|
| 2025 | 89° | 52° | 70° | — | — |
| 2024 | 89° | 55° | 72° | — | — |
| 2023 | 65° | 54° | 59° | 1.8" | — |
| 2022 | 52° | 43° | 47° | 0.38" | — |
| 2021 | 96° | 53° | 75° | — | — |
| 2020coldest | 51° | 39° | 45° | 0.05" | — |
| 2019 | 82° | 54° | 68° | 0.08" | — |
| 2018 | 89° | 51° | 70° | — | — |
| 2017 | 90° | 57° | 73° | — | — |
| 2016 | 92° | 52° | 72° | — | — |
| 2015 | 77° | 50° | 64° | — | — |
| 2014 | 68° | 44° | 56° | 1.19" | — |
| 2013 | 63° | 58° | 60° | 4.88" | — |
| 2012 | 86° | 61° | 73° | — | — |
| 2011 | 81° | 45° | 63° | — | — |
| 2010 | 82° | 44° | 63° | — | — |
| 2009 | 77° | 54° | 65° | — | — |
| 2008 | 76° | 47° | 61° | 0.1" | — |
| 2007 | 79° | 40° | 59° | — | — |
| 2006 | 72° | 47° | 59° | 0.23" | — |
| 2005 | 88° | 56° | 72° | — | — |
| 2004 | 81° | 48° | 64° | 0.13" | — |
| 2003 | 75° | 42° | 59° | — | — |
| 2002 | 70° | 40° | 55° | — | — |
| 2001 | 84° | 38° | 61° | — | — |
| 2000 | 93° | 48° | 71° | — | — |
| 1999 | 80° | 45° | 62° | — | — |
| 1998 | 88° | 58° | 73° | — | — |
| 1997 | 90° | 45° | 67° | — | — |
| 1996 | 92° | 49° | 70° | — | — |
| 1995 | 80° | 53° | 67° | — | — |
| 1994warmest | 96° | 54° | 75° | — | — |
| 1993 | 83° | 42° | 62° | — | — |
| 1992 | 77° | — | — | — | — |
| 1991 | 75° | 51° | 63° | — | — |
| 1990 | 84° | 48° | 66° | 0.05" | — |
| 1989 | 65° | 34° | 49° | 0.51" | — |
| 1988 | 89° | 50° | 70° | — | — |
| 1987 | 75° | 42° | 59° | — | — |
| 1986 | 76° | 41° | 58° | — | — |
| 1985 | 68° | 58° | 63° | 0.25" | — |
| 1984 | 94° | 49° | 71° | — | — |
| 1983 | 75° | 48° | 62° | — | — |
| 1982 | 89° | 52° | 70° | — | — |
| 1981 | 85° | 50° | 67° | 0.51" | — |
| 1980 | 74° | 49° | 61° | 0.03" | — |
| 1979 | 92° | 51° | 71° | 1.22" | — |
| 1978 | 88° | 54° | 71° | — | — |
| 1977 | 88° | 46° | 67° | — | — |
| 1976 | 84° | 46° | 65° | — | — |
| 1975 | 86° | 46° | 66° | 0.61" | — |
| 1974 | 94° | 49° | 71° | — | — |
| 1973 | 75° | 54° | 64° | 0.97" | — |
| 1972 | 82° | 47° | 64° | 0.03" | — |
| 1971 | 85° | 49° | 67° | — | — |