Environment Canada has issued a rainfall warning while the Essex Region Conservation Authority has issued a flood watch.
Between 25 and 35 mm of rain could fall today and tonight.
The rain is set to begin before noon.
The rains are tracking in on our foggy day. We could see freezing rain and thunderstorms. Potentially nasty evening commute.#sl— Sara Elliott (@SaraElliottCBC) February 20, 2014
Environment Canada said there is a chance of a brief period of snow, freezing rain or ice pellets prior to the rain because temperatures will hover just below freezing to just above.
Combined with warm temperatures, a major snow melt is expected.
Meteorologist Marie-Eve Giguere said the rain is unusual.
"It is a lot of rain, especially in the winter season. Some of it may be absorbed by the snow pack. But definitely we're expecting some accumulation of rain causing some problems; more melting and flooding potential," she said.
Heaviest rain falls from GTA to Niagara & west to Windsor. 25-50 mm of rain + snow melt + frozen ground = flooding! pic.twitter.com/j8VZJv1Wgl— CBC Weather Centre (@CBCWeather) February 20, 2014
ERCA issued a flood watch Thursday afternoon.
"There will be significant areas of the region within the City of Windsor and the entire County of Essex that will be impacted on by standing water that may in places exceed .30 cm," the authority said in a media release. "Due to roadside drains, ditches and other drainage facilities being filled with snow and ice there is a high probability of flooding over road surfaces at many locations throughout the region."
ERCA said standing water depths may be "very deep and are potentially extremely hazardous."
"People, pets and livestock should be kept away from areas of standing water," the authority said.