September is one of the warmer months of the year in Amherst, with average highs near 19.1°C and lows around 10.9°C (mean 15°C). It is about average for rainfall, averaging 85 mm of rainfall and 81% relative humidity across the period.
September is one of the warmer months of the year in Amherst. Across 45 years of records, the warmest September in Amherst was 1999 — when the month averaged 18°C — while the coldest was 1986 at 12.1°C. Typical September days reach 19.1°C with nights near 10.9°C. The long-term trend is warming, about 0.5°C per decade.
September is about average for rainfall in Amherst, averaging 85 mm of rainfall. The wettest September on record was 1996 with 189 mm, while the driest was 1985 at 18 mm.
Relative humidity in Amherst during September averages 81%. The most humid September was 2013 at 85%, and the least humid was 1995 at 71%.
September receives about 3.9 kWh/m²/day of solar energy in Amherst. The sunniest September was 2025 at 4.5 kWh/m²/day, and the cloudiest was 1996 at 3.2.
Average wind speed in Amherst during September is 1.1 m/s. The windiest Septembers were 1981 and 2004 at 1.3 m/s, while the calmest were 1999 and 2003 at 0.9 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.1°C | 14.7°C | 14.8°C | 15.5°C | 16.3°C | +2.2°C |
| Avg High | 18.1°C | 18.9°C | 18.9°C | 19.5°C | 20.5°C | +2.4°C |
| Avg Low | 10.0°C | 10.6°C | 10.7°C | 11.4°C | 12.1°C | +2.1°C |
| Avg Rain | 75 mm | 92 mm | 87 mm | 94 mm | 72 mm | -3 mm |
September temperatures in Amherst have risen by about 2°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 1.7°C (1989) to a record high of 29.5°C (2010).
Rainfall in September is about average for rainfall, averaging 85 mm, with a wettest year of 189 mm.
One of the best times to visit Amherst
September is one of the best times to visit Amherst. Expect days averaging 19.1°C and nights around 10.9°C (mean 15°C) — warmer than Amherst's yearly average — with higher rainfall (85 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 | 21.7°C | 16.6°C | 11.5°C | 26.3°C | 6.6°C | 31 mm | 74% | 1 m/s | 4.5 |
| 2024 | 20.2°C | 16.2°C | 12.2°C | 26.5°C | 9.0°C | 69 mm | 83% | 1.1 m/s | 4 |
| 2023 | 21.3°C | 17.2°C | 13.2°C | 27.1°C | 7.1°C | 67 mm | 84% | 1 m/s | 3.6 |
| 2022 | 20.0°C | 16.0°C | 12.0°C | 24.9°C | 5.5°C | 98 mm | 78% | 1.1 m/s | 4 |
| 2021 | 20.4°C | 16.5°C | 12.7°C | 24.1°C | 8.8°C | 103 mm | 84% | 1.1 m/s | 3.7 |
| 2020 | 19.5°C | 15.4°C | 11.2°C | 25.2°C | 5.9°C | 64 mm | 78% | 1.2 m/s | 4 |
| 2019 | 18.0°C | 14.0°C | 10.1°C | 23.1°C | 5.0°C | 130 mm | 81% | 1.2 m/s | 4.1 |
| 2018 | 20.0°C | 15.6°C | 11.1°C | 25.9°C | 4.9°C | 81 mm | 78% | 1.1 m/s | 4.1 |
| 2017 | 21.1°C | 16.7°C | 12.3°C | 26.5°C | 5.3°C | 64 mm | 82% | 1 m/s | 3.8 |
| 2016 | 19.5°C | 15.6°C | 11.8°C | 26.2°C | 4.4°C | 80 mm | 83% | 1.1 m/s | 3.9 |
| 2015 | 20.8°C | 16.6°C | 12.4°C | 25.8°C | 6.7°C | 104 mm | 83% | 1.1 m/s | 4.1 |
| 2014 | 19.3°C | 15.0°C | 10.7°C | 25.2°C | 4.8°C | 63 mm | 78% | 1.1 m/s | 4.2 |
| 2013 | 18.5°C | 14.7°C | 10.8°C | 23.7°C | 5.3°C | 113 mm | 85% | 1.1 m/s | 3.4 |
| 2012 | 19.5°C | 15.6°C | 11.7°C | 23.8°C | 5.5°C | 147 mm | 84% | 1.1 m/s | 3.6 |
| 2011 | 19.7°C | 15.7°C | 11.7°C | 23.6°C | 6.9°C | 44 mm | 83% | 1 m/s | 4.1 |
| 2010 | 18.9°C | 15.4°C | 11.8°C | 29.5°C | 6.0°C | 117 mm | 85% | 1.1 m/s | 3.4 |
| 2009 | 17.7°C | 13.5°C | 9.3°C | 23.5°C | 4.6°C | 65 mm | 82% | 1.2 m/s | 4.2 |
| 2008 | 18.1°C | 14.4°C | 10.7°C | 23.9°C | 4.4°C | 133 mm | 84% | 1.1 m/s | 3.7 |
| 2007 | 18.7°C | 14.6°C | 10.5°C | 24.6°C | 5.2°C | 77 mm | 78% | 1.2 m/s | 4.3 |
| 2006 | 19.0°C | 14.8°C | 10.6°C | 22.5°C | 6.0°C | 52 mm | 84% | 1 m/s | 4 |
| 2005 | 19.5°C | 15.7°C | 11.9°C | 24.4°C | 6.2°C | 121 mm | 81% | 1.2 m/s | 4 |
| 2004 | 18.0°C | 14.0°C | 9.9°C | 23.4°C | 4.7°C | 60 mm | 79% | 1.3 m/s | 4.1 |
| 2003 | 20.7°C | 16.2°C | 11.8°C | 25.9°C | 7.7°C | 50 mm | 82% | 0.9 m/s | 4.4 |
| 2002 | 19.5°C | 15.2°C | 11.0°C | 27.6°C | 2.7°C | 178 mm | 82% | 1.1 m/s | 3.8 |
| 2001 | 20.2°C | 15.6°C | 11.0°C | 26.9°C | 6.5°C | 46 mm | 78% | 1 m/s | 4.3 |
| 2000 | 18.1°C | 14.0°C | 9.9°C | 25.6°C | 3.4°C | 85 mm | 80% | 1.1 m/s | 3.9 |
| 1999 🔥 | 22.4°C | 18.0°C | 13.7°C | 28.9°C | 8.2°C | 158 mm | 81% | 0.9 m/s | 3.9 |
| 1998 | 18.3°C | 14.7°C | 11.1°C | 22.8°C | 6.2°C | 107 mm | 82% | 1 m/s | 3.3 |
| 1997 | 18.3°C | 14.4°C | 10.5°C | 23.1°C | 4.7°C | 80 mm | 84% | 1.1 m/s | 3.3 |
| 1996 🌧️ | 17.7°C | 14.2°C | 10.8°C | 26.3°C | 5.4°C | 189 mm | 83% | 1.2 m/s | 3.2 |
| 1995 | 19.0°C | 13.9°C | 8.9°C | 23.9°C | 3.1°C | 40 mm | 71% | 1.1 m/s | 4.3 |
| 1994 | 18.2°C | 14.0°C | 9.8°C | 22.3°C | 5.8°C | 53 mm | 80% | 1 m/s | 3.7 |
| 1993 | 19.5°C | 15.0°C | 10.5°C | 23.9°C | 4.4°C | 62 mm | 78% | 1.1 m/s | 3.6 |
| 1992 | 19.6°C | 15.1°C | 10.7°C | 23.7°C | 4.9°C | 30 mm | 78% | 1 m/s | 3.8 |
| 1991 | 17.4°C | 13.6°C | 9.8°C | 23.1°C | 3.2°C | 112 mm | 83% | 1.1 m/s | 3.5 |
| 1990 | 18.4°C | 14.2°C | 10.0°C | 24.1°C | 6.0°C | 90 mm | 81% | 1.1 m/s | 3.6 |
| 1989 | 18.8°C | 14.4°C | 10.0°C | 27.1°C | 1.7°C | 74 mm | 79% | 1.1 m/s | 4.1 |
| 1988 | 17.4°C | 13.4°C | 9.5°C | 22.0°C | 5.5°C | 46 mm | 79% | 1.2 m/s | 3.9 |
| 1987 | 17.8°C | 14.3°C | 10.8°C | 24.4°C | 3.2°C | 138 mm | 81% | 1.2 m/s | 3.7 |
| 1986 ❄️ | 16.3°C | 12.1°C | 7.8°C | 22.4°C | 4.0°C | 88 mm | 79% | 1.1 m/s | 3.9 |
| 1985 | 19.4°C | 15.0°C | 10.6°C | 24.5°C | 6.6°C | 18 mm | 78% | 1 m/s | 3.9 |
| 1984 | 17.4°C | 13.3°C | 9.2°C | 21.8°C | 3.3°C | 95 mm | 81% | 1.2 m/s | 4.3 |
| 1983 | 19.5°C | 15.5°C | 11.4°C | 26.0°C | 6.2°C | 52 mm | 81% | 1.1 m/s | — |
| 1982 | 18.3°C | 14.5°C | 10.6°C | 23.5°C | 6.5°C | 84 mm | 84% | 1 m/s | — |
| 1981 | 17.7°C | 14.1°C | 10.5°C | 23.1°C | 4.3°C | 80 mm | 82% | 1.3 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 19.1°C with lows near 10.9°C (mean 15°C), based on 45 years of NASA POWER data.
September averages 85 mm of rainfall in Amherst, about average for rainfall. The wettest on record was 189 mm in 1996.
The hottest September reached 29.5°C in 2010. The coldest dipped to 1.7°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2°C. Daytime highs moved from 18.5°C to 20.7°C and overnight lows from 10.5°C to 12.3°C over the same span.
September is one of the warmer months of the year in Amherst and about average for rainfall, so plan for around 19.1°C daytime highs and 10.9°C at night.
Not quite — September is the 10th coolest month in Amherst, averaging 15°C.
For September in Amherst, pack light layers you can adjust through the day, with typical highs of 19.1°C and lows of 10.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 81% — quite humid.
Average wind speed in September is 1.1 m/s. The windiest September on record averaged 1.3 m/s (1981).
The wettest September on record was 1996 with 189 mm. On average, September sees 85 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 Amherst 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.
