Thursday got off to a wet and slushy start, and the mix of heavy rainfall and melting snow is putting the city's waterways and even transit stations in peril.

Even if you aren't swimming to catch that next train, as was the case for a few unlucky commuters this morning at Long Branch GO Station, the Toronto and Region Conservation Authority is warning of flood conditions around the banks of waterways like the Don and Humber rivers.

In a flood warning issued Thursday morning, the TRCA is reporting that its watersheds were "steadily rising and have yet to peak," inundated with between 15 and 34 mm of rain overnight, worsened by another 10 to 15 mm into the morning hours.

#BREAKINGNEWS TRCA has upgraded to a #Floodwarning. Please exercise extreme caution around all river and bodies of water. Avoid driving on flooded roadways or in low-lying areas and underpasses. #ONFLOOD #ONStorm https://t.co/Glw1Q12xl0

— TRCA Flood (@TRCA_Flood) February 17, 2022

The heavy rainfall has since abated, transitioning to mixed precipitation with rain, freezing rain, ice pellets, and ultimately snowfall later this evening, but even with the falling temperatures, river water levels have the potential to stay elevated through Friday afternoon.

Among the dangers posed by the heavy precipitation and fluctuating temperatures, breaking ice has been observed in the lower Don River and lower Humber River, creating the potential for ice jams that could clog up rivers and cause flooding upstream.

The TRCA warns that the conditions are in place to see potential flooding of the Don Valley Parkway and Bayview Avenue Extension, also threatening the GO Richmond Hill Line and other lower-lying infrastructure along the Don River.

Indeed, a video emerged on Thursday morning showing that the Don River had breached its banks, the raging torrent spilling over onto the adjacent Lower Don River Trail.

Maybe avoid the lower Don River trail this morning unless you plan on swimming laps. pic.twitter.com/KSHS2dnuFX

— Anthony Farnell (@AnthonyFarnell) February 17, 2022

The TRCA's flood warning will remain in effect until Friday. Until then, it's probably a good call to stay away from fast-moving rivers that could overtake their banks at any moment, as well as bridges, culverts and dams.