September is one of the warmer months of the year in Broomfield, with average highs near 26°C and lows around 10.2°C (mean 18.1°C). It is about average for rainfall, averaging 36 mm of rainfall and 43% relative humidity across the period.
September is one of the warmer months of the year in Broomfield. Across 45 years of records, the warmest September in Broomfield was 2019 — when the month averaged 21.1°C — while the coldest was 1985 at 14.9°C. Typical September days reach 26°C with nights near 10.2°C. The long-term trend is warming, about 0.7°C per decade.
September is about average for rainfall in Broomfield, averaging 36 mm of rainfall. The wettest September on record was 2013 with 173 mm, while the driest was 2010 at 5 mm.
Relative humidity in Broomfield during September averages 43%. The most humid September was 2013 at 58%, and the least humid was 2010 at 31%.
September receives about 5.1 kWh/m²/day of solar energy in Broomfield. The sunniest September was 2010 at 6 kWh/m²/day, and the cloudiest was 2009 at 4.6.
Average wind speed in Broomfield during September is 2.1 m/s. The windiest Septembers were 1985, 1988 and 2009 at 2.4 m/s, while the calmest was 1997 at 1.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 16.9°C | 17.5°C | 17.7°C | 19.1°C | 19.8°C | +2.9°C |
| Avg High | 24.9°C | 25.3°C | 25.7°C | 27.0°C | 28.0°C | +3.1°C |
| Avg Low | 9.0°C | 9.7°C | 9.7°C | 11.3°C | 11.7°C | +2.7°C |
| Avg Rain | 32 mm | 39 mm | 33 mm | 41 mm | 30 mm | -2 mm |
September temperatures in Broomfield have risen by about 3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -8°C (1985) to a record high of 37.1°C (2019).
Rainfall in September is about average for rainfall, averaging 36 mm, with a wettest year of 173 mm.
One of the best times to visit Broomfield
September is one of the best times to visit Broomfield. Expect days averaging 26°C and nights around 10.2°C (mean 18.1°C) — warmer than Broomfield's yearly average — with moderate rainfall (36 mm), so conditions are generally comfortable for sightseeing and outdoor plans.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 26.5°C | 18.9°C | 11.4°C | 33.2°C | 7.9°C | 54 mm | 44% | 2 m/s | 4.7 |
| 2024 | 29.4°C | 21.0°C | 12.7°C | 33.8°C | 5.7°C | 28 mm | 33% | 2.2 m/s | 5.3 |
| 2023 | 27.6°C | 19.4°C | 11.3°C | 36.2°C | 6.0°C | 29 mm | 39% | 2 m/s | 5.4 |
| 2022 | 28.9°C | 20.7°C | 12.5°C | 36.9°C | 6.3°C | 27 mm | 38% | 2 m/s | 5.1 |
| 2021 | 28.9°C | 20.6°C | 12.2°C | 36.1°C | 4.3°C | 17 mm | 34% | 2 m/s | 5.4 |
| 2020 | 26.6°C | 18.3°C | 10.0°C | 37.0°C | -2.1°C | 25 mm | 36% | 2.2 m/s | 5.2 |
| 2019 🔥 | 29.5°C | 21.1°C | 12.7°C | 37.1°C | 6.0°C | 23 mm | 37% | 2.3 m/s | 5.5 |
| 2018 | 28.1°C | 20.0°C | 11.9°C | 34.6°C | 4.9°C | 16 mm | 35% | 2 m/s | 5.4 |
| 2017 | 25.6°C | 17.8°C | 10.1°C | 35.2°C | 0.8°C | 41 mm | 48% | 1.9 m/s | 4.7 |
| 2016 | 27.4°C | 19.0°C | 10.7°C | 32.1°C | 5.1°C | 10 mm | 39% | 2.1 m/s | 5.4 |
| 2015 | 28.6°C | 20.6°C | 12.7°C | 32.2°C | 6.5°C | 7 mm | 37% | 2 m/s | 5.4 |
| 2014 | 25.9°C | 18.2°C | 10.5°C | 33.5°C | -1.6°C | 51 mm | 51% | 1.9 m/s | 5.1 |
| 2013 🌧️ | 24.8°C | 18.1°C | 11.5°C | 34.4°C | 1.2°C | 173 mm | 58% | 2.2 m/s | 4.7 |
| 2012 | 26.2°C | 18.7°C | 11.3°C | 34.0°C | 7.1°C | 47 mm | 40% | 1.9 m/s | 5.1 |
| 2011 | 25.5°C | 17.9°C | 10.4°C | 35.2°C | 5.1°C | 35 mm | 44% | 2.1 m/s | 5 |
| 2010 | 28.8°C | 20.0°C | 11.1°C | 33.9°C | 6.1°C | 5 mm | 31% | 2.2 m/s | 6 |
| 2009 | 24.8°C | 17.3°C | 9.8°C | 32.4°C | 2.0°C | 35 mm | 47% | 2.4 m/s | 4.6 |
| 2008 | 25.1°C | 17.0°C | 8.9°C | 30.7°C | 4.4°C | 40 mm | 46% | 1.9 m/s | 5.4 |
| 2007 | 26.8°C | 18.8°C | 10.7°C | 31.9°C | 1.6°C | 30 mm | 43% | 2.2 m/s | 5.1 |
| 2006 | 22.9°C | 15.1°C | 7.4°C | 29.8°C | 1.5°C | 27 mm | 45% | 2.2 m/s | 5.1 |
| 2005 | 27.8°C | 19.6°C | 11.4°C | 32.7°C | 5.5°C | 14 mm | 36% | 2 m/s | 5.2 |
| 2004 | 25.3°C | 17.7°C | 10.1°C | 32.2°C | 2.7°C | 51 mm | 46% | 2.1 m/s | 5 |
| 2003 | 24.5°C | 16.2°C | 8.0°C | 30.4°C | 0.1°C | 16 mm | 43% | 2.1 m/s | 5.5 |
| 2002 | 25.9°C | 18.1°C | 10.2°C | 35.4°C | 2.2°C | 45 mm | 43% | 2.1 m/s | 4.9 |
| 2001 | 27.4°C | 19.3°C | 11.2°C | 32.5°C | 1.6°C | 29 mm | 38% | 2.1 m/s | 5.3 |
| 2000 | 26.5°C | 18.0°C | 9.5°C | 34.5°C | -2.4°C | 44 mm | 40% | 2.2 m/s | 5.2 |
| 1999 | 23.0°C | 15.1°C | 7.1°C | 30.6°C | -3.4°C | 41 mm | 47% | 2 m/s | 5.2 |
| 1998 | 28.1°C | 20.1°C | 12.2°C | 34.5°C | 5.3°C | 23 mm | 42% | 2.2 m/s | 5.5 |
| 1997 | 26.0°C | 18.5°C | 11.1°C | 30.0°C | 4.3°C | 43 mm | 51% | 1.8 m/s | 5.1 |
| 1996 | 23.7°C | 16.0°C | 8.2°C | 33.6°C | -4.1°C | 74 mm | 48% | 2.1 m/s | 4.7 |
| 1995 | 24.0°C | 16.6°C | 9.2°C | 35.1°C | -4.2°C | 60 mm | 47% | 1.9 m/s | 4.9 |
| 1994 | 26.7°C | 18.7°C | 10.7°C | 32.2°C | -0.3°C | 22 mm | 37% | 2 m/s | 5.1 |
| 1993 | 23.5°C | 15.3°C | 7.1°C | 30.9°C | -2.6°C | 56 mm | 47% | 2.2 m/s | 5.1 |
| 1992 | 26.4°C | 18.1°C | 9.8°C | 31.7°C | 3.5°C | 7 mm | 37% | 2.1 m/s | 5.5 |
| 1991 | 24.7°C | 17.1°C | 9.6°C | 30.0°C | 2.8°C | 26 mm | 47% | 2.1 m/s | 5.2 |
| 1990 | 26.7°C | 19.1°C | 11.5°C | 34.4°C | 5.5°C | 42 mm | 47% | 2.1 m/s | 5 |
| 1989 | 25.0°C | 16.9°C | 8.8°C | 33.0°C | 0.3°C | 47 mm | 45% | 2.3 m/s | 5.3 |
| 1988 | 25.2°C | 17.0°C | 8.7°C | 34.3°C | 2.4°C | 31 mm | 38% | 2.4 m/s | 5.2 |
| 1987 | 24.9°C | 17.0°C | 9.1°C | 31.2°C | 3.1°C | 19 mm | 42% | 2 m/s | 5.3 |
| 1986 | 24.1°C | 16.2°C | 8.3°C | 29.6°C | 1.7°C | 26 mm | 47% | 2.1 m/s | 4.8 |
| 1985 ❄️ | 22.7°C | 14.9°C | 7.0°C | 31.0°C | -8.0°C | 55 mm | 48% | 2.4 m/s | 4.7 |
| 1984 | 24.7°C | 16.6°C | 8.6°C | 32.4°C | -4.8°C | 21 mm | 45% | 2.1 m/s | 5 |
| 1983 | 27.1°C | 18.6°C | 10.0°C | 33.9°C | -3.3°C | 11 mm | 41% | 2.1 m/s | — |
| 1982 | 23.6°C | 16.4°C | 9.2°C | 32.1°C | 1.2°C | 60 mm | 53% | 2.1 m/s | — |
| 1981 | 26.4°C | 18.9°C | 11.4°C | 32.5°C | 5.8°C | 20 mm | 42% | 2.1 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 26°C with lows near 10.2°C (mean 18.1°C), based on 45 years of NASA POWER data.
September averages 36 mm of rainfall in Broomfield, about average for rainfall. The wettest on record was 173 mm in 2013.
The hottest September reached 37.1°C in 2019. The coldest dipped to -8°C in 1985.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 3°C. Daytime highs moved from 24.9°C to 28.3°C and overnight lows from 9.2°C to 12°C over the same span.
September is one of the warmer months of the year in Broomfield and about average for rainfall, so plan for around 26°C daytime highs and 10.2°C at night.
Not quite — September is the 9th coolest month in Broomfield, averaging 18.1°C.
For September in Broomfield, pack light layers you can adjust through the day, with typical highs of 26°C and lows of 10.2°C.
Relative humidity in September averages 43% — relatively dry.
Average wind speed in September is 2.1 m/s. The windiest September on record averaged 2.4 m/s (1985).
The wettest September on record was 2013 with 173 mm. On average, September sees 36 mm.
All figures are derived from NASA POWER (Prediction Of Worldwide Energy Resources), based on MERRA-2 satellite reanalysis, covering 1981–2025.
Explore how the weather in Broomfield behaves each September, based on 45 years of NASA POWER climate data from 1981 to 2025. This page breaks down average temperatures, rainfall, humidity, wind and solar radiation for September specifically, along with year-by-year records and how the month has changed over the decades.
