Environment Canada has issued a severe thunderstorm watch for Waterloo region.
The agency says that the conditions could create storms with powerful gusts of winds and heavy downpours.
A special weather statement has also been issued for Guelph and Wellington County as heavy rainfall accumulations of 35 to 45 mm could occur in some areas.
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The thunderstorms are expected in the late afternoon or early evening and could last past midnight.
Environment Canada warns that Canadians are killed and injured by lightning every year.
It says, “severe thunderstorm watches are issued when atmospheric conditions are favourable for the development of thunderstorms that could produce one or more of the following: large hail, damaging winds, torrential rainfall.”
Residents of Waterloo region are urged to take cover immediately if they spot threatening weather on the horizon.