SUDBURY -- Extreme heat may develop into severe thunderstorms Monday afternoon and into the evening with a threat of strong winds up to 100 km/h and torrential rain.

As the hot and humid air hangs over northeastern Ontario, bringing the daytime high temperatures to 36 C with the Humidex, Environment Canada is issuing a severe thunderstorm watch for the region Monday. Minimum overnight temperatures will be between 18 and 20 C.

Hot and humid air can also bring deteriorating air quality and cause the Air Quality Health Index to approach the high risk category.

Areas affected include:

  • Elliot Lake - Ranger Lake
  • Gogama – Foleyet
  • Greater Sudbury and vicinity
  • Kirkland Lake - Englehart
  • North Bay - Powassan - Mattawa
  • Sault Ste. Marie - St. Joseph Island
  • Searchmont - Montreal River Harbour - Batchawana Bay
  • Temiskaming Shores – Temagami
  • Timmins - Cochrane - Iroquois Falls
  • West Nipissing - French River

"Strong wind gusts can toss loose objects, damage weak buildings, break branches off trees and overturn large vehicles. Intense lightning is likely with any thunderstorm that develops. Heavy downpours can cause flash floods and water pooling on roads. Lightning kills and injures Canadians every year. Remember, when thunder roars, go indoors," says Environment Canada.

The Office of the Fire Marshal and Emergency Management recommends that you take cover immediately if threatening weather approaches.

A slightly cooler and less humid airmass will arrive in the area late on Tuesday.