Heat warnings, thunderstorm threat cover parts of northern Ontario

Monday, July 21, 2014, 11:01 AM - Tornado watches and warnings were issued in northwestern Ontario Sunday, ahead of a system that brought severe thunderstorms to the region.

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The chance for more severe storms is possible again Monday, with strong winds large hail and significant rainfall being the greatest threats.

"Current indications suggest that some areas may see 30 to 40 millimetres of rain tonight," said Environment Canada in a special weather statement early Monday. "Even higher amounts are possible locally in areas that receive several thunderstorms. The area of heavy rain is then expected to affect areas north of Lake Superior towards James Bay mainly on Tuesday."

A heat warning is also in effect for some places as a warm and humid airmass remains in place.

"Areas near the Minnesota border will likely see humidex values of near 40 during the afternoon," adds EC.

LONG RANGER: Last chance for 30 degree weather in southern Ontario this month?

Heat warnings are issued when very high temperature or humidity conditions are expected to pose an elevated risk of heat illnesses, such as heat stroke or heat exhaustion.

"Drink plenty of liquids especially water before you feel thirsty to decrease your risk of dehydration. Thirst is not a good indicator of dehydration," officials warn.

While extreme heat can put everyone at risk from heat illnesses, health risks are greatest for:

• Older adults
• Infants and young children
• People with chronic illnesses such as breathing difficulties, heart conditions or psychiatric illnesses
• People who work in the heat
• People who exercise in the heat
• People without access to air conditioning
• Homeless people.