Umbrellas and rubber boots will be a must for anyone venturing outdoors Tuesday.
Environment Canada has issued a special weather statement warning of “significant rainfall” for London-Middlesex, Chatham-Kent, Windsor-Essex, Oxford County, and Elgin County.
The rain will begin around noon as a low pressure system moves in from the southwest. Between 20 to 30 mm of rain could fall before the wet weather tapers off to a few showers in the evening.
"Locally higher rainfall amounts of 30 to 40 mm are possible in areas that receive heavy downpours during a thunderstorm," the national weather agency said in a statement.
The heavy downpours could lead to water pooling on roads. Drivers are advised to slow down and allow extra time to get where they are going.
