Weather on September 17
Longmont, CO
55 Years of Data
Avg High
79°F
Avg Low
46°F
Warmest
2000
76°F avg
Coldest
1971
37°F avg
About This Date
September 17th in Longmont, CO typically brings pleasant fall weather, with average highs around 79°F and lows near 46°F — a 33°F daily swing. Over 55 years of records, the warmest September 17th was in 2000 (76°F average), while the coldest was 1971 (37°F) — a 39°F range across recorded history. Precipitation has occurred on 16% of recorded September 17th dates, with snow falling 2% of the time (heaviest snowfall: 6"). 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 17th 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 | 78° | 45° | 61° | 0.51" | — |
| 2024 | 82° | 50° | 66° | — | — |
| 2023 | 77° | 43° | 60° | — | — |
| 2022 | 78° | 51° | 65° | 0.08" | — |
| 2021 | 93° | 48° | 71° | — | — |
| 2020 | 74° | 46° | 60° | — | — |
| 2019 | 88° | 53° | 70° | — | — |
| 2018 | 95° | 55° | 75° | — | — |
| 2017 | 65° | 46° | 55° | 0.08" | — |
| 2016 | 79° | 42° | 60° | — | — |
| 2015 | 80° | 47° | 63° | — | — |
| 2014 | 87° | 51° | 69° | — | — |
| 2013 | 82° | 49° | 65° | — | — |
| 2012 | 74° | 49° | 61° | — | — |
| 2011 | 74° | 51° | 62° | — | — |
| 2010 | 84° | 51° | 68° | — | — |
| 2009 | 77° | 50° | 64° | — | — |
| 2008 | 80° | 48° | 64° | — | — |
| 2007 | 75° | 55° | 65° | 0.28" | — |
| 2006 | 63° | 40° | 51° | — | — |
| 2005 | 85° | 52° | 68° | — | — |
| 2004 | 89° | 45° | 67° | — | — |
| 2003 | 87° | 50° | 69° | — | — |
| 2002 | 88° | 44° | 66° | — | — |
| 2001 | 78° | 46° | 62° | — | — |
| 2000warmest | 98° | 53° | 76° | — | — |
| 1999 | 77° | 36° | 56° | — | — |
| 1998 | 87° | 44° | 66° | — | — |
| 1997 | 82° | 42° | 62° | — | — |
| 1996 | 78° | 42° | 60° | — | — |
| 1995 | 85° | 44° | 64° | — | — |
| 1994 | 78° | 44° | 61° | — | — |
| 1993 | 69° | 45° | 57° | 0.36" | — |
| 1992 | 87° | — | — | — | — |
| 1991 | 73° | 40° | 56° | — | — |
| 1990 | 69° | 49° | 59° | — | — |
| 1989 | 84° | 42° | 63° | — | — |
| 1988 | 82° | 38° | 60° | — | — |
| 1987 | 74° | 45° | 59° | 0.18" | — |
| 1986 | 81° | 43° | 62° | — | — |
| 1985 | 86° | 52° | 69° | — | — |
| 1984 | 78° | 44° | 61° | — | — |
| 1983 | 93° | 43° | 68° | — | — |
| 1982 | 74° | 42° | 58° | 0.03" | — |
| 1981 | 67° | 39° | 53° | — | — |
| 1980 | 67° | 41° | 54° | — | — |
| 1979 | 85° | 43° | 64° | — | — |
| 1978 | 90° | 52° | 71° | — | — |
| 1977 | 82° | 47° | 64° | — | — |
| 1976 | 74° | 45° | 59° | — | — |
| 1975 | 86° | 51° | 69° | — | — |
| 1974 | 76° | 42° | 59° | — | — |
| 1973 | 49° | 39° | 44° | 0.03" | — |
| 1972 | 89° | 46° | 68° | — | — |
| 1971coldest | 44° | 31° | 37° | 3.94" | 6" |
55 years of data from LONGMONT 2 ESE