By Bill Deger, Meteorologist

Jul 20, 2011; 1:03 PM ET

“In addition to the threat of strong winds and hail, dangerous lightning will accompany any thunderstorm.”

As sweltering heat and humidity take over across much of the country, the threat for severe thunderstorms will be limited to the far northern tier into tonight.

Areas across the northern Plains, Upper Midwest and nearby parts of southern Canada will be targeted for the gusty storms today as a frontal boundary straddles the northern edge of the nation’s “heat dome.”

This area includes Duluth and International Falls, Minn.,; Marquette, Mich.; and the Canadian cities of Winnipeg and Thunder Bay.

Driving along Interstates 29, 35, 94 and the Trans-Canada Highway could be impacted by blinding downpours in thunderstorms.

Similar to the cluster of storms that plowed through Minnesota and Wisconsin late on Tuesday evening, powerful wind gusts greater than 60 mph can be expected in the stronger storms.

An isolated tornado cannot be ruled out either. One such tornado struck Karlstad, Minn., on Wednesday, causing extensive damage to a building and equipment inside.

Boaters enjoying a day on one of the many lakes of Minnesota or Lake Superior will need to keep an eye on the weather, and be prepared to return to safe harbor quickly at the first sign of a storm.

In addition to the threat of strong winds and hail, dangerous lightning will accompany any thunderstorm. This is especially dangerous to boaters since they could be the only object for the lightning bolt to strike within miles.

Another front will spread storms across parts of southern Ontario and Quebec overnight as well, bringing the threat for severe weather to Quebec City and even Montreal toward dusk.