Severe thunderstorm watch in effect in northeastern Ont.

Several communities in northeastern Ontario are under weather alerts for heavy rain. (File)

Several communities in northeastern Ontario are under a severe thunderstorm watch, Environment Canada said Wednesday.

Affected areas include Timmins, Cochrane, Iroquois Falls, Manitoulin Island, Kirkland Lake, Englehart, Kapuskasing, Hearst, Smooth Rock Falls, Chapleau, Missinaibi Lake, Gogama and Foleyet.

"Conditions are favourable for the development of dangerous thunderstorms that may be capable of producing damaging wind gusts, large hail and heavy rain," Environment Canada said in a statement.

Possible hazards include wind gusts near 90 km/h, nickel-size hail and heavy rain. Rain is expected to be heavies this afternoon into this evening.

"Some of these thunderstorms may become severe with strong winds, large hail and heavy rain," the statement said.

"Tornadoes also cannot be ruled out. The potential for severe thunderstorms will come to an end this evening with the passage of a cold front."

Severe thunderstorm watches are issued when atmospheric conditions are favourable for the development of thunderstorms that could produce one or more of large hail, damaging winds and torrential rainfall.

To report severe weather, send an email to [e-mail] or tweet reports using #ONStorm.