Ottawa weather in May
In May, Ottawa has daytime highs averaging 19 °C, nights around 8.1 °C, with 11 wet days. Figures are 1991–2020 climate normals.
- 18.9°C Average high
- 8.1°C Average low
- 11days Wet days
- 88mm Rainfall
- 15h Daylight
Daily temperatures through May
How May develops
Averages for the first, middle and last part of the month, from daily 1991–2020 normals. Chance of rain is the share of years in which that calendar day recorded more than 1 mm.
| Days | Avg high | Avg low | Chance of rain |
|---|---|---|---|
| 1–10 May | 17.2 °C | 6.1 °C | 37 % |
| 11–20 May | 18.0 °C | 7.3 °C | 34 % |
| 21–31 May | 21.1 °C | 10.4 °C | 38 % |
- Average highs rise from 17.2 °C early in May to 21.1 °C by the end of it.
What to expect
| Measure | Typical May | Share of the month |
|---|---|---|
| Days above 25 °C | 4.2 of 31 | 14 % |
| Days above 30 °C | 0.4 of 31 | 1 % |
| Days below 0 °C | 0.4 of 31 | 1 % |
| Days with more than 1 mm rain | 11 of 31 | 36 % |
Conditions in May
| Measure | Average |
|---|---|
| Mean temperature | 13 °C |
| Record high (1991–2020) | 34 °C |
| Record low (1991–2020) | -3.5 °C |
| Relative humidity | 66 % |
| Wind speed | 16 km/h |
| Cloud cover | 61 % |
Where Ottawa ranks in May
| Ranking | Position | Value |
|---|---|---|
| The coolest places in North America in May | 32nd of 50 | 19 °C |
May compared with the months around it
| Month | Avg high | Rainfall | Cloud |
|---|---|---|---|
| March | 2.8 °C | 71 mm | 65 % |
| April | 11.0 °C | 90 mm | 65 % |
| May | 18.9 °C | 88 mm | 61 % |
| June | 23.6 °C | 100 mm | 61 % |
| July | 25.9 °C | 97 mm | 55 % |
See all twelve months for Ottawa
- May is the 5th warmest month here.
- It is the 6th driest month of the year.
- It ranks 5th for least cloud cover.
- Days last about 15 hours from sunrise to sunset.
- It rains on 11 of 31 days — 36 % of the month.
- Nights are about 11 °C cooler than the middle of the day.
- The hottest May day on record since 1991 reached 34 °C, 15 °C above the usual daytime high.
QuestionsMay in Ottawa, answered
How warm is Ottawa in May?
Daily highs average 19 °C and nights fall to about 8.1 °C, a spread of 11 °C between afternoon and dawn. That makes May the 5th warmest month of the year here.
Does it rain much in Ottawa in May?
May averages 88 mm of rain, spread over about 11 of the 31 days — 36 % of the month. Cloud cover averages 61 % of the sky.
How long are the days in May?
Ottawa averages 15 hours between sunrise and sunset in May. Day length is computed from latitude and date, so it is exact rather than modelled — but it says nothing about how much of that time is sunny.
Data sources and method
- ERA5 / ERA5-Land reanalysis — Copernicus Climate Change Service (C3S), ECMWF. Copernicus Licence
- Open-Meteo — Open-Meteo.com. CC BY 4.0
- NOAA OISST v2.1 — NOAA Physical Sciences Laboratory. Public domain
- GeoNames — GeoNames.org. CC BY 4.0
- Normal period
- 1991–2020
- Dataset version
- era5-1991-2020-scores1.1
- Last processed
Measured values come from ERA5 reanalysis and are reproduced unchanged. Calculated by us: daylight hours, beach and comfort scores, monthly rankings, threshold day counts, chance of a wet day by date, ten-day averages within the month. Full formulas are on the methodology page.
Contains modified Copernicus Climate Change Service information 2026. Neither the European Commission nor ECMWF is responsible for any use that may be made of the Copernicus information or data it contains.