September is one of the warmer months of the year in Cape Breton, with average highs near 18.8°C and lows around 12.7°C (mean 15.8°C). It is about average for rainfall, averaging 87 mm of rainfall and 79% relative humidity across the period.
September is one of the warmer months of the year in Cape Breton. Across 45 years of records, the warmest September in Cape Breton was 1999 — when the month averaged 18.3°C — while the coldest was 1986 at 13.1°C. Typical September days reach 18.8°C with nights near 12.7°C. The long-term trend is warming, about 0.4°C per decade.
September is about average for rainfall in Cape Breton, averaging 87 mm of rainfall. The wettest September on record was 2012 with 191 mm, while the driest was 2025 at 23 mm.
Relative humidity in Cape Breton during September averages 79%. The most humid September was 2023 at 84%, and the least humid was 2025 at 73%.
September receives about 3.6 kWh/m²/day of solar energy in Cape Breton. The sunniest Septembers were 2003, 2009 and 2025 at 4.1 kWh/m²/day, and the cloudiest were 1991 and 1997 at 3.
Average wind speed in Cape Breton during September is 5.5 m/s. The windiest September was 2004 at 6.5 m/s, while the calmest was 2003 at 4.6 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.8°C | 15.6°C | 15.6°C | 16.1°C | 17.0°C | +2.2°C |
| Avg High | 17.9°C | 18.7°C | 18.7°C | 19.1°C | 20.0°C | +2.1°C |
| Avg Low | 11.8°C | 12.5°C | 12.5°C | 13.1°C | 14.1°C | +2.3°C |
| Avg Rain | 91 mm | 75 mm | 93 mm | 100 mm | 67 mm | -24 mm |
September temperatures in Cape Breton have risen by about 2°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 5.8°C (2000) to a record high of 29°C (2001).
Rainfall in September is about average for rainfall, averaging 87 mm, with a wettest year of 191 mm.
One of the best times to visit Cape Breton
September is one of the best times to visit Cape Breton. Expect days averaging 18.8°C and nights around 12.7°C (mean 15.8°C) — warmer than Cape Breton's yearly average — with higher rainfall (87 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 | 20.6°C | 17.3°C | 14.0°C | 25.1°C | 10.6°C | 23 mm | 73% | 4.8 m/s | 4.1 |
| 2024 | 20.0°C | 17.1°C | 14.3°C | 27.0°C | 11.3°C | 61 mm | 77% | 4.9 m/s | 3.9 |
| 2023 | 20.3°C | 17.3°C | 14.4°C | 26.2°C | 9.3°C | 58 mm | 84% | 4.8 m/s | 3.5 |
| 2022 | 19.3°C | 16.6°C | 14.0°C | 26.2°C | 9.0°C | 125 mm | 80% | 6.1 m/s | 3.7 |
| 2021 | 20.4°C | 17.4°C | 14.5°C | 25.7°C | 10.9°C | 85 mm | 81% | 5.7 m/s | 3.5 |
| 2020 | 19.4°C | 16.3°C | 13.2°C | 23.7°C | 8.4°C | 49 mm | 79% | 6 m/s | 3.8 |
| 2019 | 17.4°C | 14.4°C | 11.5°C | 22.4°C | 6.2°C | 93 mm | 81% | 5.7 m/s | 3.4 |
| 2018 | 19.5°C | 16.1°C | 12.7°C | 26.6°C | 6.5°C | 80 mm | 76% | 5.3 m/s | 4 |
| 2017 | 19.5°C | 16.7°C | 14.0°C | 24.4°C | 8.2°C | 112 mm | 82% | 5.4 m/s | 3.3 |
| 2016 | 18.9°C | 16.0°C | 13.1°C | 24.6°C | 8.9°C | 76 mm | 80% | 5.9 m/s | 3.6 |
| 2015 | 20.2°C | 16.9°C | 13.6°C | 24.9°C | 8.0°C | 52 mm | 82% | 5.6 m/s | 3.9 |
| 2014 | 19.0°C | 15.8°C | 12.6°C | 23.9°C | 7.7°C | 77 mm | 79% | 5.4 m/s | 3.9 |
| 2013 | 18.8°C | 15.9°C | 13.0°C | 23.7°C | 9.5°C | 107 mm | 84% | 5.8 m/s | 3.2 |
| 2012 🌧️ | 19.6°C | 16.9°C | 14.2°C | 23.2°C | 10.5°C | 191 mm | 83% | 5.6 m/s | 3.4 |
| 2011 | 19.3°C | 16.1°C | 13.0°C | 23.8°C | 8.7°C | 59 mm | 82% | 5.4 m/s | 4 |
| 2010 | 18.7°C | 15.9°C | 13.2°C | 28.9°C | 8.4°C | 157 mm | 83% | 5.9 m/s | 3.1 |
| 2009 | 17.8°C | 14.4°C | 11.0°C | 23.7°C | 7.2°C | 88 mm | 79% | 5.5 m/s | 4.1 |
| 2008 | 17.5°C | 14.8°C | 12.2°C | 22.6°C | 6.5°C | 72 mm | 83% | 5.4 m/s | 3.4 |
| 2007 | 17.9°C | 14.9°C | 11.9°C | 22.8°C | 7.0°C | 147 mm | 81% | 5.6 m/s | 3.8 |
| 2006 | 18.7°C | 15.6°C | 12.6°C | 22.5°C | 9.1°C | 42 mm | 80% | 5.3 m/s | 3.6 |
| 2005 | 20.2°C | 16.8°C | 13.5°C | 25.3°C | 9.0°C | 103 mm | 77% | 5.8 m/s | 3.6 |
| 2004 | 17.5°C | 14.6°C | 11.6°C | 24.8°C | 7.4°C | 100 mm | 77% | 6.5 m/s | 3.5 |
| 2003 | 20.6°C | 17.2°C | 13.8°C | 26.0°C | 9.7°C | 103 mm | 80% | 4.6 m/s | 4.1 |
| 2002 | 19.0°C | 15.8°C | 12.5°C | 25.2°C | 7.5°C | 130 mm | 80% | 5.7 m/s | 3.7 |
| 2001 | 19.8°C | 16.5°C | 13.3°C | 29.0°C | 8.6°C | 85 mm | 77% | 5.1 m/s | 4 |
| 2000 | 18.2°C | 15.3°C | 12.4°C | 25.8°C | 5.8°C | 65 mm | 77% | 5.7 m/s | 3.6 |
| 1999 🔥 | 21.3°C | 18.3°C | 15.3°C | 27.6°C | 9.5°C | 53 mm | 82% | 5.6 m/s | 3.8 |
| 1998 | 18.0°C | 15.2°C | 12.3°C | 21.2°C | 8.8°C | 150 mm | 83% | 5.4 m/s | 3.4 |
| 1997 | 18.2°C | 15.4°C | 12.5°C | 21.5°C | 7.1°C | 55 mm | 82% | 5.4 m/s | 3 |
| 1996 | 17.6°C | 14.8°C | 11.9°C | 25.9°C | 6.3°C | 170 mm | 80% | 6.2 m/s | 3.2 |
| 1995 | 17.6°C | 14.3°C | 11.0°C | 23.7°C | 7.1°C | 44 mm | 74% | 5.8 m/s | 3.8 |
| 1994 | 18.3°C | 15.2°C | 12.2°C | 22.6°C | 8.7°C | 60 mm | 77% | 5.4 m/s | 3.7 |
| 1993 | 19.7°C | 16.3°C | 12.9°C | 26.7°C | 8.9°C | 53 mm | 77% | 5.6 m/s | 3.4 |
| 1992 | 20.0°C | 16.5°C | 13.1°C | 24.9°C | 8.6°C | 36 mm | 74% | 5.3 m/s | 3.6 |
| 1991 | 17.8°C | 14.8°C | 11.8°C | 24.1°C | 7.6°C | 65 mm | 77% | 6.1 m/s | 3 |
| 1990 | 18.7°C | 15.5°C | 12.3°C | 23.3°C | 9.5°C | 63 mm | 76% | 5.1 m/s | 3.6 |
| 1989 | 19.1°C | 15.5°C | 12.0°C | 24.2°C | 6.1°C | 69 mm | 77% | 5.8 m/s | 3.9 |
| 1988 | 17.0°C | 13.9°C | 10.9°C | 22.6°C | 7.3°C | 51 mm | 77% | 5.9 m/s | 3.5 |
| 1987 | 18.0°C | 15.3°C | 12.5°C | 25.6°C | 7.9°C | 99 mm | 76% | 6.1 m/s | 3.7 |
| 1986 ❄️ | 16.1°C | 13.1°C | 10.1°C | 23.0°C | 7.0°C | 62 mm | 73% | 5.5 m/s | 3.7 |
| 1985 | 18.3°C | 15.1°C | 11.8°C | 25.4°C | 9.2°C | 34 mm | 77% | 4.9 m/s | 4 |
| 1984 | 17.2°C | 14.2°C | 11.2°C | 23.5°C | 6.2°C | 125 mm | 79% | 5.4 m/s | 3.9 |
| 1983 | 18.5°C | 15.7°C | 13.0°C | 24.3°C | 8.9°C | 129 mm | 81% | 5.5 m/s | — |
| 1982 | 18.5°C | 15.3°C | 12.2°C | 24.0°C | 7.7°C | 120 mm | 83% | 5 m/s | — |
| 1981 | 18.0°C | 15.4°C | 12.8°C | 23.9°C | 6.3°C | 128 mm | 82% | 6.2 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 18.8°C with lows near 12.7°C (mean 15.8°C), based on 45 years of NASA POWER data.
September averages 87 mm of rainfall in Cape Breton, about average for rainfall. The wettest on record was 191 mm in 2012.
The hottest September reached 29°C in 2001. The coldest dipped to 5.8°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°C. Daytime highs moved from 18.1°C to 20.1°C and overnight lows from 12.2°C to 14.2°C over the same span.
September is one of the warmer months of the year in Cape Breton and about average for rainfall, so plan for around 18.8°C daytime highs and 12.7°C at night.
Not quite — September is the 10th coolest month in Cape Breton, averaging 15.8°C.
For September in Cape Breton, pack light layers you can adjust through the day, with typical highs of 18.8°C and lows of 12.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 79% — quite humid.
Average wind speed in September is 5.5 m/s. The windiest September on record averaged 6.5 m/s (2004).
The wettest September on record was 2012 with 191 mm. On average, September sees 87 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 Cape Breton 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.
