Environment Canada has issued a special weather statement warning of heavy rain and thunderstorms in the GTA, and much of Southern Ontario.
They're expecting between 20 and 40 millimetres by this evening but areas with more thunderstorms could see higher amounts.
Yesterday's forecast called for heavy rain beginning around 6 a.m. but it appears it will arrive a little later than expected.
As gutters along these streets near Black Creek fill with a torrent of storm water, city contractors pull up to make sure the drainage system is working smoothly. #TOpoli pic.twitter.com/2UKc7BO58a
— NEWSTALK1010 (@NEWSTALK1010) August 21, 2018
The first parts of the storm system arrived in the GTA arrived around 6 a.m. and the heavier rain is now expected to begin around 10 a.m. and last until 2 p.m. with another blast of heavy showers possible between 4 p.m. and 8 p.m.
CTV Meteorologist Kelsey McEwen says there may be some clearing between about 2 p.m. and 4 p.m. with showers and thunderstorms possible for the rest of the day.
The Toronto and Region Conservation Authority raised its Flood Outlook from Green to Yellow before the rain moved in.
Its the second-lowest out of 4 possible levels.
The TRCA says all rivers and streams within the GTA may experience higher water levels, resulting in 'potential flooding and hazardous conditions.'
Experts with both the weather service and TRCA say thunderstorms are expected to form, and depending on where they are and how intense the rainfall is, that could further ramp up the risk of flooding.
Flooding was seen in areas across Toronto last Friday, as a storm system moved through the region.
Another bout of heavy rain the week before washed out walkways and affected transit service.
(With files from Tiffany Hendsbee and Russ Courtney)