May is one of the warmer months of the year in Wheaton, with average highs near 20.6°C and lows around 8.6°C (mean 14.6°C). It is a relatively wet time of year, averaging 107 mm of rainfall and 75% relative humidity across the period.
May is one of the warmer months of the year in Wheaton. Across 45 years of records, the warmest May in Wheaton was 2018 — when the month averaged 17.8°C — while the coldest was 1997 at 11.3°C. Typical May days reach 20.6°C with nights near 8.6°C. The long-term trend is warming, about 0.3°C per decade.
May is a relatively wet time of year in Wheaton, averaging 107 mm of rainfall. The wettest May on record was 1996 with 206 mm, while the driest was 1992 at 17 mm.
Relative humidity in Wheaton during May averages 75%. The most humid May was 1991 at 82%, and the least humid was 1988 at 65%.
May receives about 5.5 kWh/m²/day of solar energy in Wheaton. The sunniest May was 1994 at 6.7 kWh/m²/day, and the cloudiest was 1996 at 4.4.
Average wind speed in Wheaton during May is 3.3 m/s. The windiest May was 1997 at 3.9 m/s, while the calmest was 2018 at 2.8 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 14.3°C | 14.2°C | 14.5°C | 15.2°C | 15.0°C | +0.7°C |
| Avg High | 20.5°C | 20.1°C | 20.6°C | 21.0°C | 21.0°C | +0.5°C |
| Avg Low | 8.1°C | 8.2°C | 8.3°C | 9.3°C | 9.1°C | +1°C |
| Avg Rain | 95 mm | 104 mm | 109 mm | 127 mm | 91 mm | -4 mm |
May temperatures in Wheaton have risen by about 1.4°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -3.8°C (1989) to a record high of 34.2°C (2018).
Rainfall in May is a relatively wet time of year, averaging 107 mm, with a wettest year of 206 mm.
A good time to visit Wheaton
May is a good time to visit Wheaton, with days averaging 20.6°C and nights around 8.6°C (mean 14.6°C, warmer than Wheaton's yearly average) and higher rainfall. August and July 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 | 20.1°C | 14.0°C | 7.9°C | 29.4°C | 2.3°C | 52 mm | 73% | 3.3 m/s | 5.7 |
| 2024 | 23.1°C | 16.8°C | 10.6°C | 28.6°C | 6.6°C | 112 mm | 73% | 3.2 m/s | 6.3 |
| 2023 | 22.2°C | 15.3°C | 8.4°C | 31.5°C | 0.2°C | 33 mm | 66% | 3 m/s | 6.2 |
| 2022 | 21.2°C | 15.9°C | 10.6°C | 30.8°C | 1.9°C | 100 mm | 79% | 3.5 m/s | 4.9 |
| 2021 | 20.4°C | 14.7°C | 8.9°C | 30.8°C | 1.2°C | 64 mm | 69% | 3.2 m/s | 5.4 |
| 2020 | 19.0°C | 13.5°C | 8.1°C | 28.8°C | -3.2°C | 182 mm | 79% | 3.1 m/s | 5.5 |
| 2019 | 19.4°C | 13.5°C | 7.7°C | 26.1°C | 2.5°C | 189 mm | 82% | 3.2 m/s | 4.8 |
| 2018 🔥 | 23.7°C | 17.8°C | 11.8°C | 34.2°C | 5.8°C | 164 mm | 78% | 2.8 m/s | 5.7 |
| 2017 | 18.8°C | 13.3°C | 7.7°C | 28.0°C | 0.3°C | 100 mm | 79% | 3.6 m/s | 5.6 |
| 2016 | 20.6°C | 14.8°C | 9.0°C | 28.6°C | -0.9°C | 117 mm | 74% | 3.1 m/s | 5.8 |
| 2015 | 21.6°C | 15.7°C | 9.9°C | 27.7°C | 1.5°C | 117 mm | 75% | 3.5 m/s | 5.2 |
| 2014 | 20.6°C | 14.5°C | 8.4°C | 29.6°C | 2.4°C | 113 mm | 76% | 3.2 m/s | 5.7 |
| 2013 | 20.9°C | 15.2°C | 9.5°C | 29.5°C | 0.0°C | 110 mm | 79% | 3.2 m/s | 5.3 |
| 2012 | 23.5°C | 17.2°C | 10.9°C | 33.8°C | 4.8°C | 82 mm | 70% | 3.3 m/s | 6.3 |
| 2011 | 19.3°C | 13.9°C | 8.4°C | 29.9°C | -0.3°C | 135 mm | 81% | 3.6 m/s | 4.9 |
| 2010 | 21.5°C | 15.6°C | 9.6°C | 31.5°C | 0.0°C | 148 mm | 76% | 3.2 m/s | 5.4 |
| 2009 | 20.3°C | 14.2°C | 8.0°C | 27.2°C | 0.6°C | 97 mm | 76% | 3.3 m/s | 5.8 |
| 2008 | 18.5°C | 12.4°C | 6.3°C | 26.4°C | 1.2°C | 97 mm | 74% | 3.6 m/s | 5.3 |
| 2007 | 23.0°C | 16.5°C | 10.0°C | 29.7°C | 3.8°C | 45 mm | 72% | 3.4 m/s | 5.9 |
| 2006 | 20.9°C | 15.2°C | 9.4°C | 31.7°C | 2.6°C | 96 mm | 75% | 3.1 m/s | 5.4 |
| 2005 | 20.0°C | 13.8°C | 7.6°C | 27.0°C | -1.7°C | 55 mm | 69% | 3.3 m/s | 5.7 |
| 2004 | 21.5°C | 15.5°C | 9.4°C | 29.7°C | 0.0°C | 198 mm | 79% | 3.4 m/s | 5.1 |
| 2003 | 19.6°C | 13.4°C | 7.1°C | 26.7°C | 1.2°C | 125 mm | 74% | 3.7 m/s | 5.4 |
| 2002 | 18.4°C | 12.2°C | 6.0°C | 28.9°C | -1.0°C | 116 mm | 76% | 3.6 m/s | 5.3 |
| 2001 | 21.2°C | 15.2°C | 9.1°C | 31.0°C | 3.6°C | 113 mm | 73% | 3.4 m/s | 5.2 |
| 2000 | 22.4°C | 16.2°C | 10.0°C | 28.9°C | 2.7°C | 148 mm | 75% | 3.4 m/s | 4.6 |
| 1999 | 22.1°C | 16.0°C | 10.0°C | 28.6°C | 4.9°C | 100 mm | 75% | 3.6 m/s | 5.7 |
| 1998 | 23.4°C | 17.4°C | 11.5°C | 30.4°C | 6.2°C | 105 mm | 76% | 3.1 m/s | 5.9 |
| 1997 ❄️ | 17.5°C | 11.3°C | 5.0°C | 26.5°C | 0.9°C | 93 mm | 72% | 3.9 m/s | 5.5 |
| 1996 🌧️ | 18.0°C | 12.2°C | 6.4°C | 29.8°C | -0.4°C | 206 mm | 79% | 3.4 m/s | 4.4 |
| 1995 | 18.7°C | 13.3°C | 8.0°C | 25.7°C | 2.7°C | 127 mm | 76% | 3.3 m/s | 4.9 |
| 1994 | 20.5°C | 13.6°C | 6.7°C | 28.8°C | 0.1°C | 25 mm | 68% | 3 m/s | 6.7 |
| 1993 | 20.2°C | 14.5°C | 8.8°C | 26.9°C | 1.7°C | 66 mm | 78% | 3.4 m/s | 5.2 |
| 1992 | 20.1°C | 13.4°C | 6.8°C | 27.8°C | -0.2°C | 17 mm | 68% | 3.1 m/s | 6.1 |
| 1991 | 22.6°C | 17.7°C | 12.7°C | 29.9°C | 2.5°C | 134 mm | 82% | 3.1 m/s | 5.2 |
| 1990 | 17.9°C | 12.2°C | 6.5°C | 23.9°C | 0.1°C | 167 mm | 76% | 3.7 m/s | 5 |
| 1989 | 19.9°C | 13.5°C | 7.1°C | 28.2°C | -3.8°C | 91 mm | 69% | 3.3 m/s | 5.5 |
| 1988 | 22.3°C | 15.0°C | 7.7°C | 30.7°C | 1.6°C | 37 mm | 65% | 3.3 m/s | 6.6 |
| 1987 | 22.8°C | 16.5°C | 10.3°C | 28.3°C | 1.7°C | 118 mm | 74% | 3.3 m/s | 5.9 |
| 1986 | 20.5°C | 14.6°C | 8.7°C | 29.0°C | 0.4°C | 102 mm | 76% | 3.3 m/s | 5.1 |
| 1985 | 21.8°C | 15.5°C | 9.3°C | 28.5°C | 2.5°C | 71 mm | 70% | 3.8 m/s | 5.8 |
| 1984 | 18.4°C | 12.3°C | 6.2°C | 25.6°C | 0.8°C | 113 mm | 75% | 3.5 m/s | 5.2 |
| 1983 | 17.3°C | 11.7°C | 6.0°C | 23.2°C | -1.9°C | 125 mm | 79% | 3.5 m/s | — |
| 1982 | 23.3°C | 17.5°C | 11.6°C | 28.2°C | 5.8°C | 99 mm | 78% | 2.9 m/s | — |
| 1981 | 18.5°C | 12.3°C | 6.2°C | 26.5°C | -0.9°C | 100 mm | 71% | 3.5 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 20.6°C with lows near 8.6°C (mean 14.6°C), based on 45 years of NASA POWER data.
May averages 107 mm of rainfall in Wheaton, a relatively wet time of year. The wettest on record was 206 mm in 1996.
The hottest May reached 34.2°C in 2018. The coldest dipped to -3.8°C in 1989.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.4°C. Daytime highs moved from 19.9°C to 21.4°C and overnight lows from 7.9°C to 9.3°C over the same span.
May is one of the warmer months of the year in Wheaton and a relatively wet time of year, so plan for around 20.6°C daytime highs and 8.6°C at night.
Not quite — May is the 8th coolest month in Wheaton, averaging 14.6°C.
For May in Wheaton, pack light layers you can adjust through the day, with typical highs of 20.6°C and lows of 8.6°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 75% — moderately humid.
Average wind speed in May is 3.3 m/s. The windiest May on record averaged 3.9 m/s (1997).
The wettest May on record was 1996 with 206 mm. On average, May sees 107 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 Wheaton 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.
