September is one of the warmer months of the year in Billings, with average highs near 23.6°C and lows around 9°C (mean 16.3°C). It is about average for rainfall, averaging 35 mm of rainfall and 49% relative humidity across the period.
September is one of the warmer months of the year in Billings. Across 45 years of records, the warmest Septembers in Billings were 1998 and 2025 — when the month averaged 19.8°C — while the coldest was 1985 at 11.6°C. Typical September days reach 23.6°C with nights near 9°C. The long-term trend is warming, about 0.8°C per decade.
September is about average for rainfall in Billings, averaging 35 mm of rainfall. The wettest September on record was 2019 with 98 mm, while the driest was 2012 at 1 mm.
Relative humidity in Billings during September averages 49%. The most humid September was 2019 at 63%, and the least humid was 2012 at 35%.
September receives about 4.6 kWh/m²/day of solar energy in Billings. The sunniest Septembers were 2009, 2011 and 2012, among others at 5.1 kWh/m²/day, and the cloudiest were 1985 and 1986 at 3.8.
Average wind speed in Billings during September is 2.6 m/s. The windiest Septembers were 1992, 2016 and 2020 at 3 m/s, while the calmest was 2025 at 1.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.5°C | 16.3°C | 16.3°C | 16.4°C | 18.8°C | +4.3°C |
| Avg High | 21.7°C | 23.7°C | 23.7°C | 23.5°C | 26.2°C | +4.5°C |
| Avg Low | 7.3°C | 8.8°C | 8.9°C | 9.4°C | 11.5°C | +4.2°C |
| Avg Rain | 38 mm | 28 mm | 33 mm | 42 mm | 30 mm | -8 mm |
September temperatures in Billings have risen by about 5.2°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -6.4°C (1985) to a record high of 40°C (2022).
Rainfall in September is about average for rainfall, averaging 35 mm, with a wettest year of 98 mm.
One of the best times to visit Billings
September is one of the best times to visit Billings. Expect days averaging 23.6°C and nights around 9°C (mean 16.3°C) — warmer than Billings's yearly average — with moderate rainfall (35 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 | 26.9°C | 19.8°C | 12.7°C | 33.2°C | 6.9°C | 33 mm | 50% | 1.9 m/s | 4.6 |
| 2024 | 27.2°C | 19.7°C | 12.2°C | 35.3°C | 4.6°C | 62 mm | 48% | 2.5 m/s | 4.7 |
| 2023 | 25.2°C | 18.3°C | 11.4°C | 33.4°C | 6.4°C | 31 mm | 54% | 2.2 m/s | 4.6 |
| 2022 | 26.9°C | 19.7°C | 12.4°C | 40.0°C | 5.6°C | 29 mm | 44% | 2.4 m/s | 4.6 |
| 2021 | 26.0°C | 18.3°C | 10.6°C | 31.7°C | 4.0°C | 13 mm | 43% | 2.6 m/s | 4.8 |
| 2020 | 25.1°C | 17.2°C | 9.4°C | 37.3°C | -0.4°C | 15 mm | 46% | 3 m/s | 4.7 |
| 2019 🌧️ | 21.9°C | 15.5°C | 9.1°C | 35.0°C | -3.7°C | 98 mm | 63% | 2.9 m/s | 3.9 |
| 2018 | 21.2°C | 14.7°C | 8.1°C | 31.2°C | 0.8°C | 25 mm | 60% | 2.3 m/s | 4.5 |
| 2017 | 22.3°C | 15.6°C | 8.8°C | 34.3°C | -0.7°C | 83 mm | 50% | 2.3 m/s | 4.1 |
| 2016 | 22.0°C | 15.7°C | 9.4°C | 33.6°C | 3.5°C | 61 mm | 56% | 3 m/s | 4.1 |
| 2015 | 25.9°C | 18.2°C | 10.4°C | 35.3°C | 5.7°C | 14 mm | 46% | 2.6 m/s | 5 |
| 2014 | 22.5°C | 15.4°C | 8.4°C | 32.3°C | -2.5°C | 29 mm | 58% | 2.7 m/s | 4.6 |
| 2013 | 24.9°C | 18.2°C | 11.5°C | 36.5°C | 2.8°C | 65 mm | 53% | 2.6 m/s | 4.1 |
| 2012 | 26.1°C | 18.3°C | 10.5°C | 32.5°C | 4.2°C | 1 mm | 35% | 2.3 m/s | 5.1 |
| 2011 | 25.6°C | 17.6°C | 9.6°C | 31.6°C | 4.2°C | 8 mm | 45% | 2.3 m/s | 5.1 |
| 2010 | 22.6°C | 15.2°C | 7.8°C | 31.9°C | 1.9°C | 34 mm | 59% | 2.6 m/s | 4.7 |
| 2009 | 26.4°C | 18.5°C | 10.7°C | 33.7°C | 1.7°C | 20 mm | 44% | 2.8 m/s | 5.1 |
| 2008 | 21.6°C | 14.6°C | 7.5°C | 29.8°C | 2.8°C | 65 mm | 51% | 2.2 m/s | 4.4 |
| 2007 | 23.7°C | 16.1°C | 8.6°C | 35.9°C | 1.6°C | 32 mm | 48% | 2.8 m/s | 4.7 |
| 2006 | 22.5°C | 15.6°C | 8.7°C | 31.1°C | 1.0°C | 58 mm | 47% | 2.8 m/s | 4.4 |
| 2005 | 23.8°C | 16.3°C | 8.8°C | 35.2°C | 1.9°C | 25 mm | 46% | 2.7 m/s | 4.5 |
| 2004 | 22.7°C | 15.7°C | 8.7°C | 35.8°C | 1.8°C | 29 mm | 52% | 2.4 m/s | 4.5 |
| 2003 | 22.9°C | 15.8°C | 8.7°C | 35.2°C | -0.4°C | 9 mm | 42% | 2.9 m/s | 4.5 |
| 2002 | 23.5°C | 16.2°C | 8.9°C | 35.6°C | 1.7°C | 34 mm | 48% | 2.5 m/s | 4.6 |
| 2001 | 26.2°C | 18.3°C | 10.5°C | 36.2°C | 5.5°C | 27 mm | 43% | 2.4 m/s | 4.7 |
| 2000 | 23.3°C | 15.6°C | 7.9°C | 35.8°C | -4.5°C | 36 mm | 45% | 2.9 m/s | 4.5 |
| 1999 | 20.6°C | 13.6°C | 6.5°C | 29.8°C | -0.8°C | 31 mm | 49% | 2.7 m/s | 4.7 |
| 1998 🔥 | 27.2°C | 19.8°C | 12.3°C | 36.4°C | 4.3°C | 26 mm | 45% | 2.4 m/s | 4.7 |
| 1997 | 25.0°C | 17.5°C | 10.0°C | 31.4°C | 3.6°C | 14 mm | 48% | 2.8 m/s | 4.9 |
| 1996 | 22.1°C | 14.8°C | 7.6°C | 31.7°C | -1.0°C | 40 mm | 47% | 2.6 m/s | 4.6 |
| 1995 | 22.6°C | 15.4°C | 8.3°C | 34.0°C | -3.6°C | 33 mm | 50% | 2.6 m/s | 4.5 |
| 1994 | 26.1°C | 18.4°C | 10.6°C | 35.1°C | 3.2°C | 28 mm | 42% | 2.6 m/s | 4.6 |
| 1993 | 20.5°C | 13.3°C | 6.0°C | 28.7°C | -1.4°C | 29 mm | 56% | 2.6 m/s | 4.6 |
| 1992 | 23.1°C | 15.2°C | 7.2°C | 30.8°C | 0.4°C | 16 mm | 44% | 3 m/s | 4.5 |
| 1991 | 23.1°C | 15.8°C | 8.4°C | 32.4°C | -0.3°C | 61 mm | 50% | 2.5 m/s | 4.4 |
| 1990 | 27.0°C | 19.2°C | 11.4°C | 32.2°C | 4.8°C | 4 mm | 39% | 2.3 m/s | 4.9 |
| 1989 | 23.8°C | 15.8°C | 7.7°C | 31.2°C | -1.4°C | 20 mm | 44% | 2.4 m/s | 5.1 |
| 1988 | 23.2°C | 15.6°C | 8.0°C | 34.8°C | -0.2°C | 43 mm | 43% | 2.5 m/s | 4.2 |
| 1987 | 24.8°C | 16.8°C | 8.8°C | 34.5°C | 3.2°C | 17 mm | 47% | 2 m/s | 4.7 |
| 1986 | 18.2°C | 12.1°C | 6.0°C | 27.8°C | 2.1°C | 59 mm | 61% | 2.7 m/s | 3.8 |
| 1985 ❄️ | 18.0°C | 11.6°C | 5.2°C | 29.0°C | -6.4°C | 43 mm | 55% | 2.9 m/s | 3.8 |
| 1984 | 20.0°C | 12.9°C | 5.7°C | 32.9°C | -5.3°C | 35 mm | 46% | 2.9 m/s | 4.2 |
| 1983 | 20.7°C | 13.8°C | 6.9°C | 37.3°C | -6.1°C | 56 mm | 50% | 2.9 m/s | — |
| 1982 | 20.9°C | 14.1°C | 7.3°C | 32.7°C | -3.0°C | 55 mm | 54% | 2.5 m/s | — |
| 1981 | 25.7°C | 17.7°C | 9.7°C | 33.5°C | 2.2°C | 14 mm | 41% | 2.3 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 23.6°C with lows near 9°C (mean 16.3°C), based on 45 years of NASA POWER data.
September averages 35 mm of rainfall in Billings, about average for rainfall. The wettest on record was 98 mm in 2019.
The hottest September reached 40°C in 2022. The coldest dipped to -6.4°C in 1985.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 5.2°C. Daytime highs moved from 21.1°C to 26.4°C and overnight lows from 7°C to 11.9°C over the same span.
September is one of the warmer months of the year in Billings and about average for rainfall, so plan for around 23.6°C daytime highs and 9°C at night.
Not quite — September is the 9th coolest month in Billings, averaging 16.3°C.
For September in Billings, pack light layers you can adjust through the day, with typical highs of 23.6°C and lows of 9°C.
Relative humidity in September averages 49% — relatively dry.
Average wind speed in September is 2.6 m/s. The windiest September on record averaged 3 m/s (1992).
The wettest September on record was 2019 with 98 mm. On average, September sees 35 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 Billings 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.
