May is one of the warmer months of the year in Waterloo, with average highs near 18.4°C and lows around 6°C (mean 12.2°C). It is about average for rainfall, averaging 69 mm of rainfall and 75% relative humidity across the period.
May is one of the warmer months of the year in Waterloo. Across 45 years of records, the warmest May in Waterloo was 1998 — when the month averaged 15.8°C — while the coldest was 1997 at 7.5°C. Typical May days reach 18.4°C with nights near 6°C. The long-term trend is warming, about 0.2°C per decade.
May is about average for rainfall in Waterloo, averaging 69 mm of rainfall. The wettest May on record was 2000 with 175 mm, while the driest were 2005 and 2021 at 29 mm.
Relative humidity in Waterloo during May averages 75%. The most humid May was 2011 at 84%, and the least humid was 2021 at 66%.
May receives about 5.5 kWh/m²/day of solar energy in Waterloo. The sunniest May was 2023 at 6.4 kWh/m²/day, and the cloudiest was 2011 at 4.5.
Average wind speed in Waterloo during May is 3.2 m/s. The windiest May was 1997 at 3.9 m/s, while the calmest was 1982 at 2.5 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 12.3°C | 11.9°C | 11.4°C | 13.0°C | 12.6°C | +0.3°C |
| Avg High | 18.5°C | 18.2°C | 17.5°C | 19.1°C | 18.8°C | +0.3°C |
| Avg Low | 6.1°C | 5.6°C | 5.4°C | 6.9°C | 6.4°C | +0.3°C |
| Avg Rain | 63 mm | 63 mm | 86 mm | 73 mm | 52 mm | -11 mm |
May temperatures in Waterloo have risen by about 1.7°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -4.7°C (1986) to a record high of 32.2°C (2006).
Rainfall in May is about average for rainfall, averaging 69 mm, with a wettest year of 175 mm.
A good time to visit Waterloo
May is a good time to visit Waterloo, with days averaging 18.4°C and nights around 6°C (mean 12.2°C, warmer than Waterloo'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 | 17.3°C | 11.8°C | 6.3°C | 26.3°C | 0.0°C | 66 mm | 76% | 3.6 m/s | 5 |
| 2024 | 21.0°C | 14.8°C | 8.6°C | 27.7°C | 3.9°C | 75 mm | 75% | 2.7 m/s | 5.6 |
| 2023 | 18.8°C | 12.0°C | 5.2°C | 29.4°C | -1.6°C | 35 mm | 68% | 2.6 m/s | 6.4 |
| 2022 | 19.8°C | 13.6°C | 7.3°C | 29.7°C | -0.4°C | 65 mm | 75% | 3 m/s | 5.7 |
| 2021 | 19.0°C | 12.5°C | 5.9°C | 30.0°C | -1.8°C | 29 mm | 66% | 2.8 m/s | 5.7 |
| 2020 | 16.7°C | 10.9°C | 5.0°C | 29.8°C | -4.0°C | 43 mm | 73% | 3.3 m/s | 5.5 |
| 2019 | 17.1°C | 10.9°C | 4.6°C | 25.1°C | -1.6°C | 69 mm | 82% | 3.2 m/s | 4.6 |
| 2018 | 22.0°C | 14.8°C | 7.7°C | 29.2°C | -0.4°C | 69 mm | 75% | 3 m/s | 6.1 |
| 2017 | 15.7°C | 10.7°C | 5.7°C | 26.5°C | -2.1°C | 116 mm | 81% | 3.5 m/s | 5.3 |
| 2016 | 18.1°C | 12.2°C | 6.3°C | 28.4°C | -1.0°C | 50 mm | 76% | 2.7 m/s | 6 |
| 2015 | 21.0°C | 14.3°C | 7.5°C | 27.3°C | -1.2°C | 61 mm | 74% | 3 m/s | 5.7 |
| 2014 | 17.8°C | 12.1°C | 6.4°C | 25.1°C | -0.5°C | 63 mm | 80% | 3.1 m/s | 5.5 |
| 2013 | 19.1°C | 13.0°C | 6.9°C | 27.0°C | -1.2°C | 87 mm | 78% | 3.2 m/s | 6.1 |
| 2012 | 21.9°C | 15.2°C | 8.5°C | 31.6°C | 0.8°C | 39 mm | 70% | 2.7 m/s | 6.2 |
| 2011 | 17.7°C | 12.5°C | 7.2°C | 28.4°C | 0.4°C | 107 mm | 84% | 3 m/s | 4.5 |
| 2010 | 20.3°C | 14.2°C | 8.1°C | 30.4°C | -2.1°C | 66 mm | 72% | 3.2 m/s | 5.8 |
| 2009 | 18.1°C | 11.4°C | 4.6°C | 25.1°C | -2.8°C | 73 mm | 73% | 3.3 m/s | 6.1 |
| 2008 | 16.3°C | 10.3°C | 4.2°C | 23.6°C | -0.9°C | 69 mm | 74% | 3.5 m/s | 5.5 |
| 2007 | 20.2°C | 13.3°C | 6.4°C | 29.3°C | -0.5°C | 43 mm | 68% | 2.6 m/s | 6.2 |
| 2006 | 19.2°C | 13.2°C | 7.3°C | 32.2°C | 0.7°C | 49 mm | 73% | 3.1 m/s | 5.5 |
| 2005 | 16.6°C | 10.5°C | 4.5°C | 23.7°C | -1.8°C | 29 mm | 72% | 2.7 m/s | 5.6 |
| 2004 | 17.5°C | 11.6°C | 5.6°C | 25.4°C | -3.7°C | 114 mm | 83% | 3.2 m/s | 4.9 |
| 2003 | 16.2°C | 10.6°C | 5.1°C | 21.3°C | -0.3°C | 126 mm | 81% | 3.4 m/s | 4.8 |
| 2002 | 14.3°C | 8.5°C | 2.8°C | 23.5°C | -3.4°C | 78 mm | 80% | 3.7 m/s | 5.3 |
| 2001 | 18.3°C | 12.5°C | 6.7°C | 25.2°C | -0.4°C | 104 mm | 78% | 3.2 m/s | 5.5 |
| 2000 🌧️ | 18.1°C | 12.4°C | 6.7°C | 25.2°C | 1.9°C | 175 mm | 81% | 3.4 m/s | 5.1 |
| 1999 | 20.2°C | 13.6°C | 6.9°C | 29.4°C | 1.2°C | 52 mm | 70% | 3.1 m/s | 6.3 |
| 1998 🔥 | 22.2°C | 15.8°C | 9.3°C | 28.9°C | 3.0°C | 29 mm | 71% | 2.9 m/s | 6.1 |
| 1997 ❄️ | 13.3°C | 7.5°C | 1.6°C | 20.8°C | -3.0°C | 97 mm | 78% | 3.9 m/s | 5.1 |
| 1996 | 16.9°C | 10.5°C | 4.1°C | 26.6°C | -2.9°C | 60 mm | 72% | 3.1 m/s | 5.7 |
| 1995 | 18.4°C | 11.9°C | 5.4°C | 26.1°C | -1.7°C | 54 mm | 69% | 3.3 m/s | 5.3 |
| 1994 | 16.9°C | 10.5°C | 4.0°C | 27.8°C | -1.6°C | 78 mm | 73% | 3.3 m/s | 5.4 |
| 1993 | 17.8°C | 11.4°C | 5.1°C | 26.6°C | 0.6°C | 59 mm | 73% | 3.3 m/s | 5.1 |
| 1992 | 19.0°C | 12.0°C | 5.1°C | 27.1°C | -0.8°C | 41 mm | 68% | 2.7 m/s | 5.9 |
| 1991 | 20.9°C | 15.2°C | 9.5°C | 27.5°C | -0.7°C | 78 mm | 78% | 3 m/s | 5.6 |
| 1990 | 16.8°C | 10.8°C | 4.7°C | 23.7°C | -1.5°C | 82 mm | 70% | 3.6 m/s | 5.3 |
| 1989 | 18.5°C | 12.5°C | 6.6°C | 27.9°C | -0.3°C | 34 mm | 70% | 3.4 m/s | 5.1 |
| 1988 | 21.3°C | 14.1°C | 7.0°C | 31.2°C | 0.2°C | 49 mm | 66% | 3.1 m/s | 6 |
| 1987 | 21.4°C | 14.4°C | 7.4°C | 30.9°C | -1.5°C | 39 mm | 67% | 3.3 m/s | 6 |
| 1986 | 19.1°C | 13.4°C | 7.7°C | 27.2°C | -4.7°C | 71 mm | 78% | 3.3 m/s | 5.5 |
| 1985 | 18.7°C | 12.5°C | 6.3°C | 25.9°C | 1.3°C | 71 mm | 77% | 3.4 m/s | 5.9 |
| 1984 | 14.6°C | 9.0°C | 3.3°C | 23.7°C | -1.8°C | 59 mm | 80% | 3.7 m/s | 4.6 |
| 1983 | 14.8°C | 8.8°C | 2.9°C | 20.3°C | -3.6°C | 122 mm | 81% | 3.6 m/s | — |
| 1982 | 20.3°C | 14.4°C | 8.4°C | 25.2°C | 2.1°C | 66 mm | 79% | 2.5 m/s | — |
| 1981 | 17.6°C | 11.5°C | 5.5°C | 26.1°C | -2.0°C | 59 mm | 72% | 2.9 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 18.4°C with lows near 6°C (mean 12.2°C), based on 45 years of NASA POWER data.
May averages 69 mm of rainfall in Waterloo, about average for rainfall. The wettest on record was 175 mm in 2000.
The hottest May reached 32.2°C in 2006. The coldest dipped to -4.7°C in 1986.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.7°C. Daytime highs moved from 17.2°C to 19.2°C and overnight lows from 5.3°C to 6.7°C over the same span.
May is one of the warmer months of the year in Waterloo and about average for rainfall, so plan for around 18.4°C daytime highs and 6°C at night.
Not quite — May is the 8th coolest month in Waterloo, averaging 12.2°C.
For May in Waterloo, pack warm layers and a jacket for chilly mornings, with typical highs of 18.4°C and lows of 6°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 75% — moderately humid.
Average wind speed in May is 3.2 m/s. The windiest May on record averaged 3.9 m/s (1997).
The wettest May on record was 2000 with 175 mm. On average, May sees 69 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 Waterloo 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.
