Environment Canada has issued a severe thunderstorm watch for parts of southwestern Ontario, including London-Middlesex.
Thunderstorms are expected this morning and into the afternoon, and will have the potential to produce torrential rainfall.
The threat of thunderstorms will diminish late this afternoon as the upper level disturbance responsible moves away from the region.
Officials warn heavy downpours can cause flash flooding and water pooling on the roads.
The weather agency 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.
Emergency Management Ontario recommends that you take cover immediately, if threatening weather approaches.