September is one of the warmer months of the year in Granby, with average highs near 19.7°C and lows around 9.3°C (mean 14.5°C). It is about average for rainfall, averaging 97 mm of rainfall and 81% relative humidity across the period.
September is one of the warmer months of the year in Granby. Across 45 years of records, the warmest September in Granby was 2015 — when the month averaged 17.3°C — while the coldest was 1991 at 11.8°C. Typical September days reach 19.7°C with nights near 9.3°C. The long-term trend is warming, about 0.7°C per decade.
September is about average for rainfall in Granby, averaging 97 mm of rainfall. The wettest September on record was 2025 with 212 mm, while the driest was 2024 at 43 mm.
Relative humidity in Granby during September averages 81%. The most humid September was 2010 at 85%, and the least humid was 2021 at 76%.
September receives about 3.9 kWh/m²/day of solar energy in Granby. The sunniest Septembers were 2016 and 2025 at 4.5 kWh/m²/day, and the cloudiest was 1990 at 3.2.
Average wind speed in Granby during September is 0.3 m/s. The windiest September was 2020 at 0.4 m/s, while the calmest were 2023, 2024 and 2025, among others at 0.3 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 13.4°C | 13.6°C | 14.8°C | 15.4°C | 15.6°C | +2.2°C |
| Avg High | 18.5°C | 18.7°C | 20.0°C | 20.7°C | 20.9°C | +2.4°C |
| Avg Low | 8.2°C | 8.5°C | 9.5°C | 10.2°C | 10.3°C | +2.1°C |
| Avg Rain | 92 mm | 108 mm | 91 mm | 96 mm | 100 mm | +8 mm |
September temperatures in Granby have risen by about 2.3°C between 1981–1985 and 2021–2025.
September has ranged from a record low of -2.5°C (2000) to a record high of 30.2°C (1999).
Rainfall in September is about average for rainfall, averaging 97 mm, with a wettest year of 212 mm.
One of the best times to visit Granby
September is one of the best times to visit Granby. Expect days averaging 19.7°C and nights around 9.3°C (mean 14.5°C) — warmer than Granby's yearly average — with higher rainfall (97 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 🌧️ | 21.0°C | 15.3°C | 9.7°C | 25.1°C | 1.7°C | 212 mm | 79% | 0.3 m/s | 4.5 |
| 2024 | 22.1°C | 16.7°C | 11.4°C | 26.6°C | 6.6°C | 43 mm | 80% | 0.3 m/s | 4.2 |
| 2023 | 21.9°C | 16.6°C | 11.4°C | 29.7°C | 5.0°C | 77 mm | 83% | 0.3 m/s | 4 |
| 2022 | 19.7°C | 14.6°C | 9.5°C | 27.7°C | 2.3°C | 127 mm | 80% | 0.3 m/s | 3.7 |
| 2021 | 21.4°C | 16.4°C | 11.3°C | 27.2°C | 6.7°C | 78 mm | 76% | 0.3 m/s | 3.7 |
| 2020 | 19.3°C | 14.0°C | 8.7°C | 24.4°C | -0.2°C | 60 mm | 77% | 0.4 m/s | 3.6 |
| 2019 | 19.6°C | 14.2°C | 8.8°C | 26.3°C | 1.3°C | 91 mm | 82% | 0.3 m/s | 3.8 |
| 2018 | 21.7°C | 16.4°C | 11.0°C | 29.3°C | 1.5°C | 90 mm | 79% | 0.3 m/s | 3.9 |
| 2017 | 22.0°C | 16.8°C | 11.6°C | 29.3°C | 4.4°C | 62 mm | 82% | 0.3 m/s | 4.2 |
| 2016 | 21.6°C | 16.1°C | 10.6°C | 28.0°C | 2.3°C | 58 mm | 78% | 0.3 m/s | 4.5 |
| 2015 🔥 | 22.8°C | 17.3°C | 11.8°C | 29.2°C | 2.3°C | 100 mm | 80% | 0.3 m/s | 4.3 |
| 2014 | 20.1°C | 14.6°C | 9.0°C | 27.6°C | -1.6°C | 58 mm | 81% | 0.3 m/s | 3.8 |
| 2013 | 18.6°C | 13.4°C | 8.2°C | 28.8°C | 2.0°C | 113 mm | 82% | 0.3 m/s | 3.8 |
| 2012 | 19.4°C | 14.2°C | 8.9°C | 25.5°C | 2.8°C | 113 mm | 80% | 0.3 m/s | 3.9 |
| 2011 | 21.2°C | 16.3°C | 11.4°C | 28.3°C | 3.2°C | 119 mm | 84% | 0.3 m/s | 3.7 |
| 2010 | 19.6°C | 15.2°C | 10.8°C | 29.7°C | 4.6°C | 159 mm | 85% | 0.3 m/s | 3.3 |
| 2009 | 18.9°C | 13.6°C | 8.2°C | 23.9°C | 1.8°C | 58 mm | 81% | 0.3 m/s | 4.3 |
| 2008 | 20.2°C | 15.0°C | 9.7°C | 27.7°C | 1.5°C | 62 mm | 83% | 0.3 m/s | 3.7 |
| 2007 | 20.3°C | 15.0°C | 9.6°C | 28.1°C | 3.5°C | 91 mm | 81% | 0.3 m/s | 4.4 |
| 2006 | 18.8°C | 13.7°C | 8.6°C | 23.3°C | 3.5°C | 84 mm | 84% | 0.3 m/s | 3.4 |
| 2005 | 20.9°C | 15.7°C | 10.6°C | 27.2°C | 3.1°C | 125 mm | 84% | 0.3 m/s | 4 |
| 2004 | 20.2°C | 14.8°C | 9.4°C | 24.4°C | 4.2°C | 88 mm | 82% | 0.3 m/s | 4.2 |
| 2003 | 21.0°C | 15.7°C | 10.4°C | 27.0°C | 4.9°C | 79 mm | 82% | 0.3 m/s | 4 |
| 2002 | 21.4°C | 16.0°C | 10.5°C | 29.3°C | 2.7°C | 140 mm | 80% | 0.3 m/s | 4.2 |
| 2001 | 20.0°C | 14.9°C | 9.8°C | 28.1°C | 1.6°C | 60 mm | 80% | 0.3 m/s | 4.1 |
| 2000 | 18.1°C | 13.1°C | 8.0°C | 27.0°C | -2.5°C | 118 mm | 82% | 0.3 m/s | 3.7 |
| 1999 | 21.5°C | 16.4°C | 11.4°C | 30.2°C | 4.5°C | 208 mm | 82% | 0.3 m/s | 3.6 |
| 1998 | 19.8°C | 14.7°C | 9.5°C | 25.7°C | 2.2°C | 91 mm | 82% | 0.3 m/s | 3.8 |
| 1997 | 18.6°C | 13.5°C | 8.3°C | 24.4°C | 0.7°C | 54 mm | 82% | 0.3 m/s | 3.3 |
| 1996 | 19.8°C | 15.1°C | 10.3°C | 26.7°C | 2.7°C | 74 mm | 83% | 0.3 m/s | 3.7 |
| 1995 | 17.7°C | 11.9°C | 6.0°C | 24.3°C | -0.1°C | 92 mm | 78% | 0.3 m/s | 4 |
| 1994 | 18.3°C | 13.6°C | 8.8°C | 23.0°C | 4.2°C | 86 mm | 84% | 0.3 m/s | 3.6 |
| 1993 | 17.7°C | 12.7°C | 7.6°C | 26.1°C | -1.0°C | 125 mm | 81% | 0.3 m/s | 3.5 |
| 1992 | 18.6°C | 13.5°C | 8.4°C | 26.1°C | -0.4°C | 118 mm | 82% | 0.3 m/s | 3.6 |
| 1991 ❄️ | 16.8°C | 11.8°C | 6.8°C | 25.4°C | -0.7°C | 120 mm | 80% | 0.3 m/s | 3.8 |
| 1990 | 17.7°C | 12.7°C | 7.7°C | 23.6°C | 1.8°C | 108 mm | 83% | 0.3 m/s | 3.2 |
| 1989 | 19.2°C | 14.1°C | 8.9°C | 28.5°C | -0.1°C | 109 mm | 81% | 0.3 m/s | 3.7 |
| 1988 | 18.1°C | 12.8°C | 7.4°C | 25.8°C | 0.9°C | 68 mm | 79% | 0.3 m/s | 3.8 |
| 1987 | 18.1°C | 13.2°C | 8.3°C | 24.3°C | -0.8°C | 116 mm | 83% | 0.3 m/s | 3.6 |
| 1986 | 17.3°C | 12.1°C | 6.9°C | 22.8°C | 1.1°C | 137 mm | 82% | 0.3 m/s | 3.4 |
| 1985 | 19.6°C | 14.2°C | 8.8°C | 25.7°C | 2.8°C | 78 mm | 81% | 0.3 m/s | 4 |
| 1984 | 17.5°C | 12.3°C | 7.0°C | 24.0°C | -0.1°C | 56 mm | 79% | 0.3 m/s | 4.2 |
| 1983 | 20.3°C | 14.9°C | 9.5°C | 27.8°C | 3.1°C | 67 mm | 78% | 0.3 m/s | — |
| 1982 | 18.8°C | 13.9°C | 8.9°C | 25.7°C | 4.1°C | 90 mm | 84% | 0.3 m/s | — |
| 1981 | 17.6°C | 12.9°C | 8.2°C | 25.0°C | 0.3°C | 106 mm | 83% | 0.3 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 19.7°C with lows near 9.3°C (mean 14.5°C), based on 45 years of NASA POWER data.
September averages 97 mm of rainfall in Granby, about average for rainfall. The wettest on record was 212 mm in 2025.
The hottest September reached 30.2°C in 1999. The coldest dipped to -2.5°C in 2000.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.3°C. Daytime highs moved from 18.8°C to 21.2°C and overnight lows from 8.5°C to 10.7°C over the same span.
September is one of the warmer months of the year in Granby and about average for rainfall, so plan for around 19.7°C daytime highs and 9.3°C at night.
Not quite — September is the 9th coolest month in Granby, averaging 14.5°C.
For September in Granby, pack light layers you can adjust through the day, with typical highs of 19.7°C and lows of 9.3°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 81% — quite humid.
Average wind speed in September is 0.3 m/s. The windiest September on record averaged 0.4 m/s (2020).
The wettest September on record was 2025 with 212 mm. On average, September sees 97 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 Granby 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.
