Sultry tease of summer brings muggy air, storm risk to Ontario

It’s the unofficial start of summer across Ontario and the weather is certainly playing the part.

Warm southerly winds and a ridge building overhead will team up to lend a sultry feel to the air over the province for the last half of this holiday weekend.

Get ready for humidex values of 30+ with a risk for downpours in any thunderstorms that bubble up. And don’t forget the sunscreen if you’re out enjoying the warmth—that sun is brutal this time of year.

DON'T MISS: Millions at risk as land sinks beneath major coastal cities, study finds

Beware dense fog Sunday morning

It would be a seasonable setup for the end of June. But the warm air spreading over Ontario isn’t an unwelcome visitor for the middle of a long weekend.

Sunday could start with dense fog around portions of southern Ontario as warm, humid air flows over the colder lakes. Drivers around Toronto and Hamilton, as well as the Niagara Peninsula, are at risk of encountering the thick nighttime fog.

Visibilities could approach zero at times late Saturday night into early Sunday morning, so use extreme caution while driving. Conditions can change rapidly over short distances during periods of dense fog.

Steamy, stormy Sunday ahead

The fog will dissipate amid the bright sunshine. Southerly winds streaming into a low-pressure system over northern Ontario will drag warm, slightly muggy air into the province heading into our Sunday.

RELATED: Safety tips to avoid a lightning strike during a thunderstorm

Widespread warmth will cover the region through the afternoon hours. Elevated humidity levels will lend a truly summery feel to the air, pushing humidex values over 30 for communities away from the influence of the cooler lakes.

Actual air temperatures could push the 30-degree mark in spots over the next few days, including for folks in Windsor, Niagara Falls, Brockville, Cornwall, and Ottawa.

A front plowing across the Great Lakes could spark scattered thunderstorms from Windsor to Sudbury. While the dynamics aren’t in place for severe weather—a nice change from the past few days out west—some of the feistier storms could drop localized downpours, small hail, and gusty winds.

Keep an eye on the radar if you’ve got outdoor plans and stick close to sturdy shelter in case a thunderstorm approaches your area. Lightning is the most dangerous hazard in any storm. If you’re close enough to hear thunder, you’re close enough to be struck by lightning.

Sunburn risk this weekend

Folks who don’t see thunderstorms will enjoy bright sunshine that’ll help drive temperatures toward those June-like highs.

We’re firmly in sunburn season now with UV index readings pushing 9 across southwestern Ontario and in the upper single digits well into cottage country. Don’t forget to grab the sunscreen or else you might suffer a nasty burn.

Warmth sticks around into the early week

This pattern won’t stick around forever, but it’s not in any hurry to leave, either.

Monday will look like a rerun of Sunday for many communities across southern Ontario as warm and humid air continues blowing over the region.

We’ll see a renewed threat for thunderstorms across the eastern Great Lakes, including the Greater Toronto Area and up into cottage country. Lake breezes pushing into the muggy air could spark scattered thunderstorms.

Things will start to change by Wednesday as a strong low-pressure system is expected to develop near Lake Superior.

A cold front extending off this low will drag across southern Ontario, sending temperatures back toward more seasonable levels for the latter half of the workweek.

Humidity levels will drop by Thursday, and we should see temperatures back around seasonal in time for Friday.

Check back for all the latest on your forecast across Ontario this holiday weekend.

WATCH: Tips for staying safe when swimming this summer

Click here to view the video