Ontario weather in May
May is a fair month to visit Ontario: highs of 15°C (59°F) and about 73 mm (2.9 in) of rain on average. Nights average 8°C (46°F) and cloud cover 74% (NASA POWER, 2001–2025 averages). It is the 3rd wettest month of the year and the 5th warmest. Compared with April, it is warmer and about as wet; June brings highs of 21°C (70°F) and 71 mm (2.8 in) of rain.
Figures are long-term averages for Toronto, the largest city in Ontario. See below for other places.
Is May a good time to visit Ontario?
fair month Weather score 58/100.
May is a fair month in Ontario. The weather is usually best in Jun–Sep.
Does it rain a lot in Ontario in May?
Some rain is normal: about 73 mm (2.9 in) falls in an average May. It is the 3rd wettest month of the year.
How warm is Ontario in May?
Days average 15°C (59°F) and nights 8°C (46°F).
Ontario weather by month
| Month | High | Low | Rain | Cloud | Weather |
|---|---|---|---|---|---|
| January | 0°C (31°F) | -5°C (23°F) | 54 mm | 81% | least pleasant |
| February | 0°C (32°F) | -5°C (22°F) | 49 mm | 79% | least pleasant |
| March | 4°C (38°F) | -2°C (28°F) | 53 mm | 74% | least pleasant |
| April | 9°C (48°F) | 2°C (36°F) | 71 mm | 75% | least pleasant |
| May | 15°C (59°F) | 8°C (46°F) | 73 mm | 74% | fair |
| June | 21°C (70°F) | 14°C (58°F) | 71 mm | 68% | best |
| July | 25°C (77°F) | 18°C (65°F) | 75 mm | 64% | best |
| August | 25°C (76°F) | 19°C (65°F) | 59 mm | 62% | best |
| September | 21°C (70°F) | 15°C (60°F) | 66 mm | 60% | best |
| October | 14°C (57°F) | 9°C (48°F) | 74 mm | 74% | fair |
| November | 8°C (46°F) | 3°C (37°F) | 66 mm | 75% | least pleasant |
| December | 3°C (37°F) | -2°C (29°F) | 63 mm | 81% | least pleasant |
Sources: 2001–2025 monthly averages from NASA POWER (MERRA-2 reanalysis). Page updated . How we rate months
Weather across Ontario in May
Weather can differ a lot within Ontario: coasts, hills and mountains each have their own climate.
| Place | High | Low | Rain | Weather |
|---|---|---|---|---|
| Toronto | 15°C (59°F) | 8°C (46°F) | 73 mm | fair |
| Ottawa | 19°C (65°F) | 7°C (44°F) | 85 mm | best |
| Mississauga | 15°C (59°F) | 8°C (46°F) | 73 mm | fair |
| Brampton | 19°C (66°F) | 7°C (44°F) | 74 mm | best |
| Hamilton | 19°C (66°F) | 7°C (44°F) | 74 mm | best |
| London | 19°C (67°F) | 7°C (45°F) | 66 mm | best |
| Etobicoke | 15°C (59°F) | 8°C (46°F) | 73 mm | fair |
| Markham | 18°C (64°F) | 7°C (44°F) | 67 mm | best |
| Vaughan | 18°C (64°F) | 7°C (44°F) | 67 mm | best |
| Kitchener | 18°C (65°F) | 6°C (43°F) | 73 mm | best |
| Windsor | 20°C (68°F) | 8°C (47°F) | 97 mm | best |
| Oakville | 15°C (59°F) | 8°C (46°F) | 73 mm | fair |