May is one of the warmer months of the year in Ajax, with average highs near 17.3°C and lows around 6.7°C (mean 12°C). It is about average for rainfall, averaging 61 mm of rainfall and 74% relative humidity across the period.
May is one of the warmer months of the year in Ajax. Across 45 years of records, the warmest May in Ajax was 1998 — when the month averaged 15.5°C — while the coldest was 1997 at 8.3°C. Typical May days reach 17.3°C with nights near 6.7°C. The long-term trend is warming, about 0.2°C per decade.
May is about average for rainfall in Ajax, averaging 61 mm of rainfall. The wettest May on record was 2002 with 136 mm, while the driest was 2005 at 17 mm.
Relative humidity in Ajax during May averages 74%. The most humid May was 2004 at 85%, and the least humid was 2021 at 64%.
May receives about 5.5 kWh/m²/day of solar energy in Ajax. The sunniest May was 2023 at 6.3 kWh/m²/day, and the cloudiest was 1984 at 4.4.
Average wind speed in Ajax during May is 3 m/s. The windiest May was 1997 at 3.8 m/s, while the calmest was 2007 at 2.3 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 12.1°C | 11.8°C | 11.0°C | 12.8°C | 12.8°C | +0.7°C |
| Avg High | 17.5°C | 17.3°C | 16.1°C | 18.0°C | 18.1°C | +0.6°C |
| Avg Low | 6.7°C | 6.3°C | 6.0°C | 7.5°C | 7.4°C | +0.7°C |
| Avg Rain | 57 mm | 60 mm | 88 mm | 52 mm | 39 mm | -18 mm |
May temperatures in Ajax have risen by about 2°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -2.8°C (2020) to a record high of 30.3°C (1987).
Rainfall in May is about average for rainfall, averaging 61 mm, with a wettest year of 136 mm.
A good time to visit Ajax
May is a good time to visit Ajax, with days averaging 17.3°C and nights around 6.7°C (mean 12°C, warmer than Ajax's yearly average) and moderate rainfall. July and August are marginally more temperate, but May still suits most travellers.
| Year | Avg High | Avg Temp | Avg Low | Hottest Day | Coldest Day | Rainfall | Humidity | Wind | Solar |
|---|---|---|---|---|---|---|---|---|---|
| 2025 | 17.0°C | 12.1°C | 7.1°C | 24.4°C | 2.1°C | 75 mm | 75% | 3.4 m/s | 5 |
| 2024 | 20.1°C | 15.1°C | 10.0°C | 27.3°C | 5.5°C | 37 mm | 74% | 2.8 m/s | 5.7 |
| 2023 | 18.6°C | 12.5°C | 6.5°C | 29.7°C | 1.0°C | 25 mm | 66% | 2.5 m/s | 6.3 |
| 2022 | 19.1°C | 13.6°C | 8.1°C | 28.2°C | 1.7°C | 40 mm | 71% | 2.9 m/s | 5.7 |
| 2021 | 18.1°C | 12.4°C | 6.7°C | 27.8°C | -1.3°C | 20 mm | 64% | 3 m/s | 5.7 |
| 2020 | 15.9°C | 10.9°C | 5.9°C | 27.8°C | -2.8°C | 37 mm | 71% | 3.2 m/s | 5.4 |
| 2019 | 14.7°C | 9.9°C | 5.1°C | 20.9°C | 1.4°C | 57 mm | 82% | 3 m/s | 4.6 |
| 2018 | 20.1°C | 14.0°C | 7.9°C | 27.7°C | 1.2°C | 47 mm | 76% | 2.8 m/s | 6.1 |
| 2017 | 14.8°C | 10.8°C | 6.7°C | 24.3°C | 0.2°C | 119 mm | 82% | 3.3 m/s | 5 |
| 2016 | 18.0°C | 12.5°C | 7.1°C | 28.0°C | 0.3°C | 32 mm | 74% | 2.6 m/s | 6 |
| 2015 | 20.1°C | 14.2°C | 8.3°C | 26.5°C | 0.2°C | 34 mm | 69% | 3.1 m/s | 5.8 |
| 2014 | 17.0°C | 11.9°C | 6.8°C | 24.5°C | 1.3°C | 50 mm | 78% | 2.9 m/s | 5.4 |
| 2013 | 18.8°C | 13.4°C | 7.9°C | 27.5°C | 1.2°C | 44 mm | 71% | 3.1 m/s | 6.1 |
| 2012 | 20.5°C | 14.8°C | 9.1°C | 29.4°C | 2.9°C | 28 mm | 69% | 2.6 m/s | 6 |
| 2011 | 16.5°C | 12.0°C | 7.6°C | 24.9°C | 1.4°C | 64 mm | 84% | 3 m/s | 4.5 |
| 2010 | 19.5°C | 14.1°C | 8.8°C | 30.1°C | -0.5°C | 49 mm | 72% | 3.1 m/s | 5.7 |
| 2009 | 16.1°C | 10.8°C | 5.5°C | 22.1°C | 0.1°C | 74 mm | 77% | 3.4 m/s | 6.1 |
| 2008 | 14.7°C | 9.9°C | 5.1°C | 21.3°C | 0.3°C | 78 mm | 78% | 3.3 m/s | 5.3 |
| 2007 | 18.1°C | 12.3°C | 6.4°C | 26.7°C | 1.2°C | 59 mm | 73% | 2.3 m/s | 6.2 |
| 2006 | 17.8°C | 12.9°C | 8.1°C | 29.9°C | 0.3°C | 64 mm | 76% | 3 m/s | 5.5 |
| 2005 | 15.8°C | 10.5°C | 5.3°C | 23.5°C | -0.5°C | 17 mm | 73% | 2.5 m/s | 5.9 |
| 2004 | 15.7°C | 11.0°C | 6.2°C | 21.6°C | -1.8°C | 114 mm | 85% | 3 m/s | 4.9 |
| 2003 | 14.7°C | 10.2°C | 5.7°C | 19.1°C | 1.0°C | 117 mm | 82% | 3.1 m/s | 4.8 |
| 2002 🌧️ | 13.4°C | 8.5°C | 3.6°C | 21.1°C | -0.9°C | 136 mm | 80% | 3.6 m/s | 5.1 |
| 2001 | 17.5°C | 12.4°C | 7.2°C | 24.0°C | 1.4°C | 103 mm | 77% | 3.1 m/s | 5.6 |
| 2000 | 16.9°C | 11.9°C | 7.0°C | 24.8°C | 1.9°C | 117 mm | 81% | 3.1 m/s | 4.9 |
| 1999 | 19.4°C | 13.6°C | 7.9°C | 28.6°C | 3.0°C | 52 mm | 69% | 2.8 m/s | 6.1 |
| 1998 🔥 | 21.1°C | 15.5°C | 10.0°C | 27.7°C | 4.9°C | 44 mm | 71% | 2.9 m/s | 5.8 |
| 1997 ❄️ | 13.2°C | 8.3°C | 3.3°C | 20.0°C | -1.3°C | 46 mm | 74% | 3.8 m/s | 4.9 |
| 1996 | 15.1°C | 9.9°C | 4.8°C | 23.2°C | -1.6°C | 65 mm | 73% | 2.9 m/s | 5.6 |
| 1995 | 17.8°C | 12.1°C | 6.3°C | 26.8°C | -0.6°C | 41 mm | 67% | 3.3 m/s | 5.4 |
| 1994 | 16.0°C | 10.4°C | 4.8°C | 26.9°C | -0.3°C | 90 mm | 73% | 3.2 m/s | 5.3 |
| 1993 | 17.4°C | 11.7°C | 5.9°C | 27.0°C | 1.9°C | 51 mm | 71% | 3.1 m/s | 5.1 |
| 1992 | 16.9°C | 11.4°C | 5.8°C | 25.1°C | 0.9°C | 58 mm | 71% | 2.4 m/s | 6.1 |
| 1991 | 20.1°C | 14.7°C | 9.2°C | 26.4°C | -0.4°C | 63 mm | 76% | 3 m/s | 5.5 |
| 1990 | 15.5°C | 10.4°C | 5.4°C | 22.4°C | -0.3°C | 88 mm | 73% | 3.3 m/s | 5 |
| 1989 | 17.4°C | 12.2°C | 7.0°C | 25.2°C | 0.5°C | 61 mm | 72% | 3.2 m/s | 4.9 |
| 1988 | 19.9°C | 13.7°C | 7.6°C | 29.6°C | 1.2°C | 51 mm | 66% | 2.9 m/s | 5.8 |
| 1987 | 20.3°C | 14.2°C | 8.2°C | 30.3°C | 0.1°C | 25 mm | 65% | 3.2 m/s | 5.9 |
| 1986 | 18.9°C | 13.6°C | 8.2°C | 28.0°C | -2.3°C | 47 mm | 74% | 3.3 m/s | 5.4 |
| 1985 | 17.8°C | 12.5°C | 7.1°C | 23.3°C | 0.2°C | 57 mm | 74% | 3.3 m/s | 5.7 |
| 1984 | 13.6°C | 8.9°C | 4.2°C | 21.7°C | -1.3°C | 65 mm | 80% | 3.6 m/s | 4.4 |
| 1983 | 13.9°C | 9.1°C | 4.3°C | 19.2°C | -1.8°C | 91 mm | 80% | 3.4 m/s | — |
| 1982 | 19.0°C | 13.5°C | 8.1°C | 24.3°C | 2.8°C | 42 mm | 76% | 2.6 m/s | — |
| 1981 | 16.7°C | 11.3°C | 5.8°C | 24.1°C | -0.8°C | 71 mm | 72% | 2.8 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 17.3°C with lows near 6.7°C (mean 12°C), based on 45 years of NASA POWER data.
May averages 61 mm of rainfall in Ajax, about average for rainfall. The wettest on record was 136 mm in 2002.
The hottest May reached 30.3°C in 1987. The coldest dipped to -2.8°C in 2020.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 2°C. Daytime highs moved from 16.2°C to 18.6°C and overnight lows from 5.9°C to 7.7°C over the same span.
May is one of the warmer months of the year in Ajax and about average for rainfall, so plan for around 17.3°C daytime highs and 6.7°C at night.
Not quite — May is the 8th coolest month in Ajax, averaging 12°C.
For May in Ajax, pack warm layers and a jacket for chilly mornings, with typical highs of 17.3°C and lows of 6.7°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 74% — moderately humid.
Average wind speed in May is 3 m/s. The windiest May on record averaged 3.8 m/s (1997).
The wettest May on record was 2002 with 136 mm. On average, May sees 61 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 May, 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 May specifically, along with year-by-year records and how the month has changed over the decades.
