After heavy rains overnight and more precipitation to come, the Toronto and Region Conservation Authority has placed the city under flood watch until Saturday, warning that flooding along waterways could cause hazardous conditions.

As of Friday morning, the south end of Bayview Avenue is closed and part of the Richmond Hill GO Train line is shut down after between 20 and 40 millimetres of rain fell in just a few hours overnight.

Bayview Avenue is closed between River Street and King Street East.

Flooding on the Richmond Hill GO Train line has also led to a portion of track being closed, with the GO Transit webpage listing the following service impacts, which they say could add 30-45 minutes to the usual travel time:

GO Transit says that track closures on the Richmond Hill line will add 30-45 minutes to commute times. (Tony Smyth/CBC)

The Gormley GO 07:15 - Union Station 08:13 train will only serve Gormley GO, Richmond Hill GO and Langstaff GO stations where it will then take an alternative route to Union Station.

The Gormley GO 07:45 - Union Station 08:43 train will only serve Gormley GO, Richmond Hill GO and Langstaff GO stations where it will then take an alternative route to Union Station.

The Gormley GO 08:15 - Union Station 09:13 train will only serve Gormley GO, Richmond Hill GO and Langstaff GO stations where it will then take an alternative route to Union Station

Passengers at the Old Cummer and Oriole GO stations may use their GO Tickets or Presto Card on the TTC at a staffed entrace at the Finch, Sheppard or Leslie subway station(s).

More rain coming

The TRCA release warns that another rain system is headed for Toronto, with 20-25 millimetres of rain expected around 8 a.m.

"The water levels in many of TRCA's watercourses are still rising and have yet to peak, including the Don River," reads the release.

High river levels, combined with the already-high lake levels, could result in flooding along low-lying roads and trails, including the Don Valley Parkway, it said.

The TRCA is recommending that people exercise caution around bodies of water and "avoid driving in low-lying areas and roadways, particularly at underpasses, as well as the shoreline."

The rain is expected to subside by Friday night, and Saturday is expected to be mainly sunny.