September is one of the warmer months of the year in Ajax, with average highs near 21.7°C and lows around 12°C (mean 16.9°C). It is about average for rainfall, averaging 65 mm of rainfall and 72% relative humidity across the period.
September is one of the warmer months of the year in Ajax. Across 45 years of records, the warmest September in Ajax was 2015 — when the month averaged 19.6°C — while the coldest was 1993 at 13.7°C. Typical September days reach 21.7°C with nights near 12°C. The long-term trend is warming, about 0.9°C per decade.
September is about average for rainfall in Ajax, averaging 65 mm of rainfall. The wettest September on record was 1986 with 151 mm, while the driest was 2023 at 13 mm.
Relative humidity in Ajax during September averages 72%. The most humid September was 1981 at 81%, and the least humid was 1991 at 65%.
September receives about 4.1 kWh/m²/day of solar energy in Ajax. The sunniest September was 2005 at 4.7 kWh/m²/day, and the cloudiest were 1993 and 2006 at 3.2.
Average wind speed in Ajax during September is 3 m/s. The windiest September was 2010 at 3.7 m/s, while the calmest were 2017 and 2025 at 2.3 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 15.7°C | 15.6°C | 17.2°C | 18.0°C | 18.4°C | +2.7°C |
| Avg High | 20.5°C | 20.5°C | 22.1°C | 22.8°C | 23.3°C | +2.8°C |
| Avg Low | 10.9°C | 10.7°C | 12.3°C | 13.2°C | 13.5°C | +2.6°C |
| Avg Rain | 80 mm | 68 mm | 69 mm | 53 mm | 48 mm | -32 mm |
September temperatures in Ajax have risen by about 2.7°C between 1981–1985 and 2021–2025.
September has ranged from a record low of 0.4°C (1989) to a record high of 33.2°C (2023).
Rainfall in September is about average for rainfall, averaging 65 mm, with a wettest year of 151 mm.
One of the best times to visit Ajax
September is one of the best times to visit Ajax. Expect days averaging 21.7°C and nights around 12°C (mean 16.9°C) — warmer than Ajax's yearly average — with moderate rainfall (65 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 | 24.0°C | 18.7°C | 13.5°C | 27.1°C | 8.7°C | 36 mm | 65% | 2.3 m/s | 4.5 |
| 2024 | 24.3°C | 19.4°C | 14.4°C | 28.3°C | 8.6°C | 66 mm | 72% | 2.7 m/s | 4.3 |
| 2023 | 24.3°C | 19.0°C | 13.7°C | 33.2°C | 7.5°C | 13 mm | 68% | 2.6 m/s | 4.4 |
| 2022 | 22.3°C | 17.6°C | 13.0°C | 29.7°C | 5.1°C | 50 mm | 71% | 2.8 m/s | 3.9 |
| 2021 | 23.2°C | 18.4°C | 13.6°C | 26.4°C | 7.8°C | 86 mm | 69% | 3.5 m/s | 4.3 |
| 2020 | 22.0°C | 17.3°C | 12.6°C | 27.6°C | 4.7°C | 34 mm | 69% | 3.3 m/s | 4.2 |
| 2019 | 22.6°C | 17.9°C | 13.2°C | 28.7°C | 9.0°C | 49 mm | 73% | 3 m/s | 3.8 |
| 2018 | 23.6°C | 19.2°C | 14.7°C | 32.3°C | 8.3°C | 58 mm | 72% | 3.1 m/s | 3.9 |
| 2017 | 24.4°C | 19.1°C | 13.9°C | 32.7°C | 6.8°C | 39 mm | 69% | 2.3 m/s | 4.6 |
| 2016 | 24.3°C | 19.5°C | 14.7°C | 30.7°C | 7.9°C | 43 mm | 67% | 3 m/s | 4.4 |
| 2015 🔥 | 24.3°C | 19.6°C | 14.9°C | 32.0°C | 7.6°C | 86 mm | 72% | 2.8 m/s | 4.2 |
| 2014 | 21.7°C | 16.8°C | 11.8°C | 27.7°C | 5.3°C | 51 mm | 73% | 2.9 m/s | 4.1 |
| 2013 | 21.5°C | 16.5°C | 11.4°C | 31.4°C | 4.5°C | 47 mm | 70% | 2.9 m/s | 4.1 |
| 2012 | 21.7°C | 17.0°C | 12.2°C | 28.5°C | 6.0°C | 44 mm | 68% | 3 m/s | 4.2 |
| 2011 | 22.5°C | 18.0°C | 13.5°C | 30.6°C | 5.8°C | 65 mm | 73% | 3 m/s | 3.8 |
| 2010 | 21.2°C | 16.7°C | 12.1°C | 31.1°C | 7.3°C | 51 mm | 72% | 3.7 m/s | 3.6 |
| 2009 | 22.1°C | 17.2°C | 12.2°C | 26.1°C | 5.0°C | 50 mm | 70% | 2.9 m/s | 4.4 |
| 2008 | 21.8°C | 17.1°C | 12.4°C | 29.9°C | 7.5°C | 69 mm | 75% | 2.6 m/s | 4 |
| 2007 | 22.9°C | 17.8°C | 12.7°C | 30.5°C | 6.1°C | 52 mm | 70% | 3 m/s | 4.5 |
| 2006 | 20.0°C | 15.8°C | 11.7°C | 25.9°C | 5.0°C | 98 mm | 77% | 3.3 m/s | 3.2 |
| 2005 | 24.6°C | 19.1°C | 13.7°C | 30.9°C | 7.2°C | 77 mm | 69% | 3.4 m/s | 4.7 |
| 2004 | 23.0°C | 17.9°C | 12.8°C | 28.0°C | 5.7°C | 63 mm | 74% | 2.8 m/s | 4.6 |
| 2003 | 21.1°C | 16.5°C | 11.8°C | 26.7°C | 5.8°C | 72 mm | 73% | 3.2 m/s | 4.1 |
| 2002 | 24.2°C | 19.0°C | 13.8°C | 32.0°C | 9.6°C | 51 mm | 68% | 2.9 m/s | 4.6 |
| 2001 | 20.7°C | 15.8°C | 10.9°C | 28.5°C | 4.8°C | 77 mm | 72% | 3 m/s | 4.3 |
| 2000 | 20.6°C | 15.9°C | 11.1°C | 29.8°C | 1.2°C | 76 mm | 72% | 3.4 m/s | 4 |
| 1999 | 22.8°C | 17.8°C | 12.8°C | 31.1°C | 3.3°C | 84 mm | 69% | 3 m/s | 4.2 |
| 1998 | 22.9°C | 17.8°C | 12.7°C | 30.5°C | 5.9°C | 58 mm | 70% | 2.9 m/s | 4.3 |
| 1997 | 20.8°C | 15.8°C | 10.8°C | 26.8°C | 3.5°C | 81 mm | 73% | 3.5 m/s | 3.9 |
| 1996 | 20.8°C | 16.3°C | 11.8°C | 28.8°C | 4.4°C | 85 mm | 75% | 3 m/s | 3.4 |
| 1995 | 19.4°C | 14.2°C | 8.9°C | 27.5°C | 4.5°C | 47 mm | 69% | 2.8 m/s | 4.1 |
| 1994 | 20.7°C | 15.6°C | 10.5°C | 27.9°C | 6.3°C | 62 mm | 73% | 3 m/s | 3.9 |
| 1993 ❄️ | 18.3°C | 13.7°C | 9.1°C | 27.1°C | 0.5°C | 79 mm | 74% | 3.2 m/s | 3.2 |
| 1992 | 18.9°C | 14.3°C | 9.8°C | 25.4°C | 2.6°C | 83 mm | 79% | 3.4 m/s | 4.1 |
| 1991 | 20.3°C | 15.3°C | 10.3°C | 29.4°C | 1.7°C | 44 mm | 65% | 3.1 m/s | 4.2 |
| 1990 | 20.1°C | 15.3°C | 10.5°C | 27.3°C | 4.1°C | 61 mm | 74% | 3.1 m/s | 3.6 |
| 1989 | 20.9°C | 16.0°C | 11.0°C | 27.6°C | 0.4°C | 75 mm | 72% | 2.9 m/s | 4 |
| 1988 | 20.9°C | 15.6°C | 10.3°C | 27.4°C | 5.8°C | 49 mm | 70% | 3.5 m/s | 4.3 |
| 1987 | 20.2°C | 15.6°C | 11.0°C | 26.2°C | 5.4°C | 79 mm | 76% | 2.9 m/s | 3.7 |
| 1986 🌧️ | 19.2°C | 14.7°C | 10.2°C | 25.1°C | 3.5°C | 151 mm | 78% | 3.1 m/s | 3.6 |
| 1985 | 22.0°C | 17.0°C | 12.0°C | 29.5°C | 5.4°C | 56 mm | 73% | 2.9 m/s | 4.5 |
| 1984 | 19.4°C | 14.6°C | 9.8°C | 25.4°C | 2.9°C | 80 mm | 72% | 3.2 m/s | 4 |
| 1983 | 22.8°C | 17.5°C | 12.2°C | 31.9°C | 5.8°C | 47 mm | 67% | 3.3 m/s | — |
| 1982 | 20.8°C | 15.7°C | 10.5°C | 28.3°C | 4.9°C | 53 mm | 72% | 2.7 m/s | — |
| 1981 | 18.4°C | 14.6°C | 10.8°C | 26.4°C | 0.9°C | 126 mm | 81% | 3.2 m/s | — |
Actual recorded September data for each year, 1981–2025 — sourced from NASA POWER.
The average high in September is around 21.7°C with lows near 12°C (mean 16.9°C), based on 45 years of NASA POWER data.
September averages 65 mm of rainfall in Ajax, about average for rainfall. The wettest on record was 151 mm in 1986.
The hottest September reached 33.2°C in 2023. The coldest dipped to 0.4°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average September temperatures have risen by about 2.7°C. Daytime highs moved from 20.7°C to 23.6°C and overnight lows from 11.1°C to 13.6°C over the same span.
September is one of the warmer months of the year in Ajax and about average for rainfall, so plan for around 21.7°C daytime highs and 12°C at night.
Not quite — September is the 9th coolest month in Ajax, averaging 16.9°C.
For September in Ajax, pack light layers you can adjust through the day, with typical highs of 21.7°C and lows of 12°C. Bring an umbrella or light rain jacket too.
Relative humidity in September averages 72% — moderately humid.
Average wind speed in September is 3 m/s. The windiest September on record averaged 3.7 m/s (2010).
The wettest September on record was 1986 with 151 mm. On average, September sees 65 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 Ajax 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.
