September is one of the warmer months of the year in Summerside, with average highs near 18.3°C and lows around 11.9°C (mean 15.1°C). It is about average for rainfall, averaging 87 mm of rainfall and 81% relative humidity across the period.
September is one of the warmer months of the year in Summerside. Across 45 years of records, the warmest September in Summerside was 1999 — when the month averaged 18.1°C — while the coldest was 1986 at 12.1°C. Typical September days reach 18.3°C with nights near 11.9°C. The long-term trend is warming, about 0.4°C per decade.
September is about average for rainfall in Summerside, averaging 87 mm of rainfall. The wettest September on record was 2012 with 177 mm, while the driest was 1985 at 23 mm.
Relative humidity in Summerside during September averages 81%. The most humid September was 2023 at 86%, and the least humid was 1995 at 70%.
September receives about 3.7 kWh/m²/day of solar energy in Summerside. The sunniest Septembers were 2003 and 2025 at 4.3 kWh/m²/day, and the cloudiest were 1991 and 1997 at 3.1.
Average wind speed in Summerside during September is 3.9 m/s. The windiest Septembers were 1987, 1988 and 2004 at 4.5 m/s, while the calmest was 2003 at 3.2 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.2°C | 15.0°C | 14.9°C | 15.5°C | 16.3°C | +2.1°C |
| Avg High | 17.3°C | 18.3°C | 18.1°C | 18.6°C | 19.4°C | +2.1°C |
| Avg Low | 11.0°C | 11.7°C | 11.7°C | 12.4°C | 13.2°C | +2.2°C |
| Avg Rain | 84 mm | 78 mm | 89 mm | 101 mm | 78 mm | -6 mm |
September temperatures in Summerside have risen by about 1.8°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 4.5°C (1981) to a record high of 28°C (2010).
Rainfall in September is about average for rainfall, averaging 87 mm, with a wettest year of 177 mm.
One of the best times to visit Summerside
September is one of the best times to visit Summerside. Expect days averaging 18.3°C and nights around 11.9°C (mean 15.1°C) — warmer than Summerside'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 | 20.1°C | 16.5°C | 12.9°C | 25.6°C | 9.4°C | 38 mm | 75% | 3.5 m/s | 4.3 |
| 2024 | 19.3°C | 16.3°C | 13.3°C | 25.0°C | 10.8°C | 65 mm | 83% | 3.6 m/s | 3.8 |
| 2023 | 20.2°C | 17.0°C | 13.9°C | 25.8°C | 9.0°C | 53 mm | 86% | 3.3 m/s | 3.6 |
| 2022 | 18.9°C | 16.0°C | 13.1°C | 24.1°C | 8.2°C | 123 mm | 79% | 4 m/s | 3.8 |
| 2021 | 19.5°C | 16.4°C | 13.4°C | 23.1°C | 9.4°C | 115 mm | 84% | 4.1 m/s | 3.7 |
| 2020 | 18.6°C | 15.4°C | 12.3°C | 24.3°C | 8.0°C | 74 mm | 78% | 4.2 m/s | 3.9 |
| 2019 | 17.0°C | 14.0°C | 11.1°C | 22.0°C | 7.9°C | 145 mm | 81% | 4.2 m/s | 3.6 |
| 2018 | 18.8°C | 15.6°C | 12.3°C | 24.5°C | 6.2°C | 111 mm | 78% | 3.8 m/s | 4 |
| 2017 | 19.6°C | 16.3°C | 13.0°C | 24.7°C | 7.0°C | 72 mm | 84% | 3.7 m/s | 3.5 |
| 2016 | 18.6°C | 15.7°C | 12.8°C | 24.7°C | 7.9°C | 83 mm | 83% | 4 m/s | 3.7 |
| 2015 | 19.7°C | 16.4°C | 13.0°C | 25.0°C | 7.4°C | 92 mm | 83% | 3.8 m/s | 3.9 |
| 2014 | 18.5°C | 15.1°C | 11.8°C | 24.9°C | 7.1°C | 70 mm | 78% | 4 m/s | 4 |
| 2013 | 18.1°C | 14.9°C | 11.7°C | 22.6°C | 8.0°C | 116 mm | 85% | 4.1 m/s | 3.2 |
| 2012 🌧️ | 18.9°C | 15.8°C | 12.7°C | 23.8°C | 9.0°C | 177 mm | 83% | 4 m/s | 3.6 |
| 2011 | 18.8°C | 15.6°C | 12.4°C | 22.6°C | 8.3°C | 28 mm | 84% | 3.4 m/s | 4.1 |
| 2010 | 18.3°C | 15.5°C | 12.8°C | 28.0°C | 7.1°C | 112 mm | 84% | 3.9 m/s | 3.2 |
| 2009 | 17.1°C | 13.7°C | 10.4°C | 22.4°C | 6.8°C | 58 mm | 81% | 4.1 m/s | 4.2 |
| 2008 | 17.2°C | 14.5°C | 11.7°C | 23.7°C | 6.8°C | 140 mm | 84% | 4 m/s | 3.4 |
| 2007 | 17.6°C | 14.5°C | 11.5°C | 23.6°C | 8.3°C | 87 mm | 79% | 4.1 m/s | 4 |
| 2006 | 18.2°C | 15.0°C | 11.8°C | 21.5°C | 8.2°C | 57 mm | 84% | 3.5 m/s | 3.8 |
| 2005 | 18.7°C | 15.8°C | 12.9°C | 24.2°C | 8.0°C | 150 mm | 82% | 4.3 m/s | 3.7 |
| 2004 | 17.0°C | 14.0°C | 11.0°C | 23.2°C | 7.3°C | 59 mm | 79% | 4.5 m/s | 3.7 |
| 2003 | 19.6°C | 16.1°C | 12.6°C | 24.4°C | 9.0°C | 51 mm | 84% | 3.2 m/s | 4.3 |
| 2002 | 18.7°C | 15.2°C | 11.8°C | 26.7°C | 6.4°C | 170 mm | 81% | 4 m/s | 3.6 |
| 2001 | 19.1°C | 15.9°C | 12.6°C | 25.5°C | 8.6°C | 38 mm | 77% | 3.7 m/s | 4.1 |
| 2000 | 17.5°C | 14.2°C | 11.0°C | 24.0°C | 5.5°C | 82 mm | 79% | 4 m/s | 3.8 |
| 1999 🔥 | 21.7°C | 18.1°C | 14.5°C | 26.4°C | 9.2°C | 118 mm | 81% | 3.5 m/s | 3.9 |
| 1998 | 18.0°C | 15.1°C | 12.1°C | 22.6°C | 8.1°C | 94 mm | 80% | 3.8 m/s | 3.4 |
| 1997 | 18.0°C | 14.9°C | 11.7°C | 22.2°C | 6.1°C | 57 mm | 81% | 3.9 m/s | 3.1 |
| 1996 | 17.1°C | 14.6°C | 12.0°C | 25.4°C | 8.5°C | 160 mm | 81% | 4.3 m/s | 3.3 |
| 1995 | 18.1°C | 14.2°C | 10.3°C | 23.2°C | 5.0°C | 47 mm | 70% | 3.8 m/s | 4 |
| 1994 | 17.6°C | 14.3°C | 11.0°C | 20.8°C | 6.4°C | 54 mm | 79% | 3.4 m/s | 3.8 |
| 1993 | 19.2°C | 15.4°C | 11.7°C | 24.1°C | 7.4°C | 46 mm | 76% | 4.2 m/s | 3.6 |
| 1992 | 19.2°C | 15.5°C | 11.8°C | 23.3°C | 6.4°C | 23 mm | 76% | 3.8 m/s | 3.7 |
| 1991 | 16.8°C | 13.8°C | 10.9°C | 22.8°C | 6.2°C | 92 mm | 82% | 4 m/s | 3.1 |
| 1990 | 17.8°C | 14.4°C | 11.0°C | 23.0°C | 8.2°C | 89 mm | 81% | 3.9 m/s | 3.5 |
| 1989 | 17.9°C | 14.4°C | 10.9°C | 25.2°C | 5.2°C | 83 mm | 80% | 4.1 m/s | 3.9 |
| 1988 | 16.8°C | 13.7°C | 10.5°C | 22.0°C | 7.6°C | 57 mm | 80% | 4.5 m/s | 3.6 |
| 1987 | 17.3°C | 14.5°C | 11.7°C | 23.0°C | 5.2°C | 146 mm | 81% | 4.5 m/s | 3.6 |
| 1986 ❄️ | 15.4°C | 12.1°C | 8.9°C | 21.1°C | 6.6°C | 92 mm | 79% | 3.7 m/s | 3.6 |
| 1985 | 18.5°C | 15.2°C | 11.8°C | 23.6°C | 9.1°C | 23 mm | 78% | 3.4 m/s | 4 |
| 1984 | 16.9°C | 13.7°C | 10.4°C | 21.7°C | 5.6°C | 97 mm | 81% | 4.2 m/s | 4 |
| 1983 | 18.5°C | 15.4°C | 12.4°C | 25.0°C | 8.1°C | 78 mm | 82% | 3.8 m/s | — |
| 1982 | 17.3°C | 14.2°C | 11.2°C | 22.0°C | 7.7°C | 92 mm | 85% | 3.4 m/s | — |
| 1981 | 17.0°C | 14.3°C | 11.6°C | 21.8°C | 4.5°C | 91 mm | 84% | 4.3 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 18.3°C with lows near 11.9°C (mean 15.1°C), based on 45 years of NASA POWER data.
September averages 87 mm of rainfall in Summerside, about average for rainfall. The wettest on record was 177 mm in 2012.
The hottest September reached 28°C in 2010. The coldest dipped to 4.5°C in 1981.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 1.8°C. Daytime highs moved from 17.6°C to 19.6°C and overnight lows from 11.5°C to 13.3°C over the same span.
September is one of the warmer months of the year in Summerside and about average for rainfall, so plan for around 18.3°C daytime highs and 11.9°C at night.
Not quite — September is the 10th coolest month in Summerside, averaging 15.1°C.
For September in Summerside, pack light layers you can adjust through the day, with typical highs of 18.3°C and lows of 11.9°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 81% — quite humid.
Average wind speed in September is 3.9 m/s. The windiest September on record averaged 4.5 m/s (1987).
The wettest September on record was 2012 with 177 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 Summerside 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.
