With thunderstorms, high winds and significant rainfall in tonight's forecast, the Toronto Region Conservation Authority (TRCA) has issued a flood watch for Toronto.

The watch was issued just after 11 a.m. Monday and will remain in effect through to Tuesday.

Environment Canada has also issued a severe thunderstorm watch for the city with winds up to 90 km/h possible.

The warning comes after 20 to 40 millimetres of rain fell in a 24-hour-period, causing high lake levels. Monday's forecast calls for isolated thunderstorms and about 25 millimetres more rain.

A look at high water levels in The Beach following a flood watch issued by the Toronto Region Conservation Authority. 0:52

"All rivers within the GTA will be experiencing high flows and water levels, resulting in unsafe conditions," the statement reads. "There is the potential that water levels will exceed its riverbanks resulting in flooding."

"The water levels in many of TRCA's watercourses are still rising and have yet to peak, including the Don River. There is a potential for flooding of roads and trails along streams and rivers including the Bayview Avenue extension."

The statement asks that people take care with children and pets near waterways or at the shoreline.

TRCA has issued a <a href="https://twitter.com/hashtag/FloodWatch?src=hash">#FloodWatch</a> message for rivers and streams. Details here: <a href="https://t.co/gQrTR4nNWW">https://t.co/gQrTR4nNWW</a> <a href="https://twitter.com/hashtag/ONSTORM?src=hash">#ONSTORM</a> <a href="https://twitter.com/hashtag/ONFLOOD?src=hash">#ONFLOOD</a> <a href="https://t.co/3KMqRA4MRM">pic.twitter.com/3KMqRA4MRM</a> —@TRCA_Flood

And while only minimal amounts of rain are expected Tuesday and Wednesday, heavy rain is expected later in the week with 10 to 15 millimetres coming Thursday and a whopping 35 to 45 millimetres in Friday's forecast.

A dog walker steps carefully around the shores of a swollen Lake Ontario in Toronto's Beach neighbourhood. After a wet weekend and with more rain coming, the Toronto and Region Conservation Authority has issued a flood watch for the city. (Martin Trainor/CBC)

​Flooding reported in Bowmanville, spotted at Woodbine Beach

East of Toronto in Bowmanville, Clarington Emergency and Fire Services were called in to help residents in the Cedar Crest Beach area deal with flooding caused by a lake surge.

A news release from the municipality of Clarington says eight to 10 properties had some flooding. A group of full- and part-time firefighters, 10 operations staff and about 40 neighbours came together to help. Hundreds of sandbags were used to form a wall to protect properties and homes.

Clarington's fire chief warned residents to be careful, particularly with children and pets, near the lakeshore and to ensure their sump pumps were working.