Rainfall warnings in effect for Windsor-Essex, Chatham-Kent, Sarnia with flooding possible

Heavy rainfall is in the forecast for Windsor-Essex, Chatham-Kent and Sarnia, as well as much of the rest of southwestern Ontario, Environment Canada warns. 

The weather agency issued a heavy rainfall warning for Wednesday morning lasting into Thursday, with between 30 and 50 millimetres of rain possible. 

"The ground, already near saturation, has little ability to absorb further rainfall," Environment Canada says, adding that locally, more rainfall is possible if thunderstorms repeatedly hit an area. 

The rain will begin Wednesday morning over Windsor and travel up to the Golden Horseshoe on Wednesday afternoon, Environment Canada says. 

'"With thunderstorms expected, rainfall amounts may exceed 50 millimetres over some areas, particularly over southwestern Ontario," Environment Canada warned. "Rain will end from west to east Wednesday night into early Thursday morning."

Freezing rain Wednesday in Sarnia also possible

There's also the chance for a brief period of freezing rain in the Sarnia area Wednesday morning or in the afternoon.

The special weather statement lists Sarnia, Petrolia and parts of western Lambton County.

"Surfaces such as highways, roads, walkways and parking lots may become icy, slippery and hazardous," Environment Canada posted online. 

"A brief period of freezing rain is possible before a transition to rain."

Conservation authorities warn of flooding

Environment Canada advises residents to consult their local conservation authorities for any information about flooding. 

The Lower Thames Valley Conservation Area, which includes Essex, Lakeshore and Chatham-Kent and stretches up to London, says localized ponding, standing water and flooding are expected. 

"Smaller watercourses that drain into the Thames River, or to the lakes, should be expected to rise and some could spill their banks into adjacent low-lying areas," the conservation authority warned, noting some waterways are still running higher than usual because of last weekend's rain. 

The Essex Region Conservation Authority has also issued a flood watch.

In Chatham, the conservation area warns that flooding of the sidewalk along the river in downtown is expected. 

The St. Clair Region Conservation Authority is also warning for people to be cautious near watercourses.

It's located in southwestern Ontario, and includes the Sydenham River watershed and smaller ones draining directly into southern Lake Huron, the St. Clair River and northeastern Lake St. Clair.

Flood forecaster and warning co-ordinator Emily De Cloet said levels across the region are already elevated from 10 to 25 millimetres of rain from last weekend.

"There is a risk of thunderstorms this evening and overnight, which could bring higher amounts of rainfall to localized areas, as well as the possibility for high intensity rainfall in a short period of time, which could lead to increased runoff and urban flooding," said De Cloet.