Sudbury Weather Forecast – Cool, Cloudy, and Turning Rainy
A Breezy Start with Clouds Gathering
Greater Sudbury, ON – Wednesday, May 21, 2025: Northern Ontario is serving up a classic spring cocktail today — a cool breeze, heavy clouds, and the occasional tease of rain. As of 6:00 AM at Greater Sudbury Airport, the thermometer reads a brisk 4.8°C, and it feels just as crisp as it sounds. The skies are partly cloudy, with the barometric pressure at 101.6 kPa and falling, signaling that wet weather is closing in. Humidity is at a noticeable 79%, while winds from the northeast are blowing at 20 km/h, adding a chilly bite to the air.
Cloud cover is expected to thicken throughout the day, making for a generally overcast Wednesday. The temperature will climb to a high of 13°C, so don’t expect a major warm-up. With a UV index of 5, you might get a few sun breaks, but your sunglasses can probably take the day off.
Showers Brewing Overnight, Rain Moves In by Thursday
Tonight, skies stay cloudy with a 40% chance of showers developing, turning to more consistent rain before dawn. Winds from the northeast continue at 20 km/h but will ease up later this evening. Expect the overnight low to settle at 7°C — a mild night by northern standards, but with that damp air creeping in, it’ll feel cooler.
Thursday brings full-on rain with 10 to 15 mm expected, and temperatures hovering near 9°C all day. Winds shift to the east at 20 km/h before calming in the afternoon. The UV index drops to 1, so this is a day for rain jackets, not sunglasses. Thursday night carries on with showers and a low of 6°C.
By Friday, it’s still umbrella season in Sudbury, with more showers in the forecast and a daytime high of just 11°C. Cloudy skies continue into the night with a 30% chance of lingering showers and a low around +5°C.
What to Wear?
Today calls for cozy layers and a windbreaker to handle that northeast breeze. A waterproof shell will come in handy tonight and definitely tomorrow. If you’re heading out later in the week, keep that rain gear on standby — and maybe pack an extra pair of dry socks just in case.
Historic Temperatures for May 21
Sudbury’s weather history for today shows a record high of 30.2°C, a far cry from today’s modest forecast. The record low was a frosty -4.3°C, which makes this morning’s 5°C feel downright balmy in comparison.
Northern Ontario Weather Trivia
Did you know Sudbury has more lakes than any other city in Canada? Over 300 of them! Which means the city gets its fair share of lake-effect weather — particularly when spring storms blow through. If you’re wondering why it feels damper here, blame the lakes… and maybe your cousin who left the back door open.
