May is one of the warmer months of the year in Ottawa, with average highs near 18.3°C and lows around 6.4°C (mean 12.4°C). It is about average for rainfall, averaging 83 mm of rainfall and 77% relative humidity across the period.
May is one of the warmer months of the year in Ottawa. Across 45 years of records, the warmest May in Ottawa was 1998 — when the month averaged 15.8°C — while the coldest was 1997 at 9°C. Typical May days reach 18.3°C with nights near 6.4°C. The long-term trend is warming, about 0.3°C per decade.
May is about average for rainfall in Ottawa, averaging 83 mm of rainfall. The wettest May on record was 2017 with 175 mm, while the driest was 2021 at 27 mm.
Relative humidity in Ottawa during May averages 77%. The most humid May was 2011 at 83%, and the least humid was 2021 at 71%.
May receives about 5.3 kWh/m²/day of solar energy in Ottawa. The sunniest May was 2023 at 6.3 kWh/m²/day, and the cloudiest was 1984 at 4.1.
Average wind speed in Ottawa during May is 0.3 m/s. The windiest Mays were 1990, 1997 and 2013, among others at 0.4 m/s, while the calmest were 2023, 2024 and 2025, among others at 0.3 m/s.
Ranked against the other 11 months using 1981–2025 averages.
| Metric | 1980s | 1990s | 2000s | 2010s | 2020s | Change |
|---|---|---|---|---|---|---|
| Avg Temp | 12.1°C | 12.1°C | 11.8°C | 13.1°C | 12.8°C | +0.7°C |
| Avg High | 17.8°C | 18.2°C | 17.7°C | 19.1°C | 19.0°C | +1.2°C |
| Avg Low | 6.3°C | 6.0°C | 5.9°C | 7.1°C | 6.6°C | +0.3°C |
| Avg Rain | 94 mm | 72 mm | 93 mm | 86 mm | 61 mm | -33 mm |
May temperatures in Ottawa have risen by about 1.8°C between 1981–1985 and 2021–2025.
May has ranged from a record low of -4.4°C (2020) to a record high of 31.5°C (1987).
Rainfall in May is about average for rainfall, averaging 83 mm, with a wettest year of 175 mm.
A good time to visit Ottawa
May is a good time to visit Ottawa, with days averaging 18.3°C and nights around 6.4°C (mean 12.4°C, warmer than Ottawa's yearly average) and higher 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 | 18.4°C | 12.6°C | 6.8°C | 25.8°C | -1.0°C | 63 mm | 78% | 0.3 m/s | 4.6 |
| 2024 | 20.5°C | 15.0°C | 9.6°C | 29.1°C | 5.1°C | 79 mm | 77% | 0.3 m/s | 5.2 |
| 2023 | 18.4°C | 11.7°C | 5.1°C | 31.3°C | -2.4°C | 57 mm | 72% | 0.3 m/s | 6.3 |
| 2022 | 20.9°C | 14.2°C | 7.4°C | 30.4°C | -0.5°C | 92 mm | 75% | 0.3 m/s | 5.8 |
| 2021 | 18.7°C | 12.6°C | 6.5°C | 29.7°C | -2.9°C | 27 mm | 71% | 0.3 m/s | 5.8 |
| 2020 | 17.3°C | 10.9°C | 4.4°C | 30.6°C | -4.4°C | 48 mm | 74% | 0.3 m/s | 6 |
| 2019 | 16.0°C | 10.4°C | 4.9°C | 21.3°C | -1.7°C | 100 mm | 80% | 0.3 m/s | 4.6 |
| 2018 | 20.4°C | 13.6°C | 6.8°C | 26.6°C | 0.1°C | 61 mm | 77% | 0.3 m/s | 5.9 |
| 2017 🌧️ | 16.4°C | 11.5°C | 6.6°C | 27.5°C | -3.2°C | 175 mm | 82% | 0.3 m/s | 4.6 |
| 2016 | 18.8°C | 12.4°C | 6.1°C | 28.4°C | -2.4°C | 43 mm | 76% | 0.3 m/s | 5.8 |
| 2015 | 21.2°C | 14.5°C | 7.7°C | 28.3°C | -2.2°C | 80 mm | 74% | 0.3 m/s | 5.7 |
| 2014 | 18.9°C | 12.9°C | 7.0°C | 26.9°C | -1.4°C | 95 mm | 78% | 0.3 m/s | 5.5 |
| 2013 | 19.8°C | 13.6°C | 7.4°C | 28.0°C | 0.4°C | 92 mm | 74% | 0.4 m/s | 5.5 |
| 2012 | 21.1°C | 14.9°C | 8.7°C | 28.5°C | 2.3°C | 61 mm | 76% | 0.3 m/s | 5.6 |
| 2011 | 18.1°C | 12.9°C | 7.7°C | 27.4°C | -0.6°C | 111 mm | 83% | 0.3 m/s | 4.5 |
| 2010 | 20.4°C | 14.3°C | 8.1°C | 30.8°C | -2.2°C | 45 mm | 74% | 0.3 m/s | 5.8 |
| 2009 | 17.1°C | 11.2°C | 5.4°C | 25.5°C | -0.8°C | 96 mm | 76% | 0.3 m/s | 5.2 |
| 2008 | 16.9°C | 11.0°C | 5.1°C | 22.3°C | 0.6°C | 79 mm | 75% | 0.3 m/s | 5.8 |
| 2007 | 18.9°C | 12.2°C | 5.4°C | 28.2°C | -1.6°C | 61 mm | 74% | 0.3 m/s | 6 |
| 2006 | 18.6°C | 13.5°C | 8.3°C | 30.7°C | -2.8°C | 107 mm | 80% | 0.3 m/s | 4.9 |
| 2005 | 16.5°C | 10.5°C | 4.5°C | 25.8°C | -3.6°C | 45 mm | 76% | 0.3 m/s | 5.2 |
| 2004 | 18.4°C | 12.1°C | 5.9°C | 26.8°C | -3.5°C | 89 mm | 78% | 0.3 m/s | 5.2 |
| 2003 | 17.7°C | 12.0°C | 6.2°C | 24.3°C | -2.3°C | 135 mm | 77% | 0.3 m/s | 5 |
| 2002 | 15.6°C | 9.8°C | 4.1°C | 25.4°C | -1.3°C | 105 mm | 76% | 0.3 m/s | 4.9 |
| 2001 | 19.4°C | 13.7°C | 7.9°C | 26.8°C | 1.0°C | 77 mm | 78% | 0.3 m/s | 5.2 |
| 2000 | 17.9°C | 11.9°C | 6.0°C | 26.0°C | -0.9°C | 135 mm | 80% | 0.3 m/s | 4.7 |
| 1999 | 21.4°C | 14.6°C | 7.9°C | 28.6°C | 0.1°C | 48 mm | 73% | 0.3 m/s | 6 |
| 1998 🔥 | 22.0°C | 15.8°C | 9.6°C | 27.3°C | 3.4°C | 61 mm | 73% | 0.3 m/s | 5.8 |
| 1997 ❄️ | 14.5°C | 9.0°C | 3.4°C | 22.3°C | -3.4°C | 78 mm | 76% | 0.4 m/s | 4.9 |
| 1996 | 16.6°C | 10.2°C | 3.9°C | 25.7°C | -0.7°C | 66 mm | 74% | 0.3 m/s | 5.8 |
| 1995 | 18.0°C | 11.8°C | 5.6°C | 26.1°C | -3.6°C | 82 mm | 76% | 0.3 m/s | 5 |
| 1994 | 17.0°C | 10.9°C | 4.8°C | 27.4°C | -1.1°C | 96 mm | 78% | 0.3 m/s | 5.3 |
| 1993 | 17.9°C | 12.2°C | 6.5°C | 27.8°C | 0.4°C | 74 mm | 78% | 0.3 m/s | 5 |
| 1992 | 18.2°C | 11.6°C | 5.0°C | 26.7°C | -0.9°C | 69 mm | 75% | 0.3 m/s | 6.1 |
| 1991 | 20.1°C | 14.1°C | 8.1°C | 26.2°C | -0.3°C | 81 mm | 78% | 0.3 m/s | 5.4 |
| 1990 | 16.1°C | 10.6°C | 5.2°C | 23.9°C | -1.9°C | 64 mm | 77% | 0.4 m/s | 5 |
| 1989 | 18.4°C | 13.0°C | 7.5°C | 28.1°C | 1.2°C | 106 mm | 80% | 0.3 m/s | 4.5 |
| 1988 | 19.2°C | 13.1°C | 6.9°C | 27.1°C | 0.1°C | 50 mm | 76% | 0.3 m/s | 5.4 |
| 1987 | 18.6°C | 12.3°C | 6.1°C | 31.5°C | -3.7°C | 73 mm | 76% | 0.3 m/s | 5.2 |
| 1986 | 18.7°C | 13.2°C | 7.7°C | 27.3°C | -3.3°C | 137 mm | 79% | 0.3 m/s | 5 |
| 1985 | 17.8°C | 11.7°C | 5.6°C | 25.9°C | -2.5°C | 60 mm | 75% | 0.3 m/s | 5.6 |
| 1984 | 15.1°C | 10.0°C | 5.0°C | 24.8°C | -2.4°C | 111 mm | 79% | 0.3 m/s | 4.1 |
| 1983 | 15.3°C | 9.8°C | 4.2°C | 22.0°C | -3.2°C | 128 mm | 80% | 0.4 m/s | — |
| 1982 | 19.6°C | 13.5°C | 7.4°C | 25.5°C | 1.8°C | 55 mm | 79% | 0.3 m/s | — |
| 1981 | 17.9°C | 11.9°C | 5.9°C | 25.9°C | -2.2°C | 123 mm | 77% | 0.3 m/s | — |
Actual recorded May data for each year, 1981–2025 — sourced from NASA POWER.
The average high in May is around 18.3°C with lows near 6.4°C (mean 12.4°C), based on 45 years of NASA POWER data.
May averages 83 mm of rainfall in Ottawa, about average for rainfall. The wettest on record was 175 mm in 2017.
The hottest May reached 31.5°C in 1987. The coldest dipped to -4.4°C in 2020.
Comparing the earliest years on record (1981–1985) with the most recent (2021–2025), average May temperatures have risen by about 1.8°C. Daytime highs moved from 17.1°C to 19.4°C and overnight lows from 5.6°C to 7.1°C over the same span.
May is one of the warmer months of the year in Ottawa and about average for rainfall, so plan for around 18.3°C daytime highs and 6.4°C at night.
Not quite — May is the 8th coolest month in Ottawa, averaging 12.4°C.
For May in Ottawa, pack warm layers and a jacket for chilly mornings, with typical highs of 18.3°C and lows of 6.4°C. Bring an umbrella or light rain jacket too.
Relative humidity in May averages 77% — quite humid.
Average wind speed in May is 0.3 m/s. The windiest May on record averaged 0.4 m/s (1983).
The wettest May on record was 2017 with 175 mm. On average, May sees 83 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 Ottawa 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.
