Environment Canada has lifted a tornado warning for Halton Hills and Milton and replaced it with a severe thunderstorm warning.
Shortly before 3:30 p.m., the weather agency said its meteorologists were tracking a severe storm that was possibly producing a tornado.
At 3:51 p.m., the tornado warning was replaced with a severe thunderstorm warning. It then downgraded to a severe thunderstorm watch.
Elsewhere in the GTA, Toronto, Mississauga, Brampton, Caledon, northern York Region, Vaughan, Richmond Hill and Markham are under a severe thunderstorm watch.
A warning means storms are imminent or occurring, while a watch means conditions are in place for storms to possibly develop.
“Thunderstorms are developing across portions of southern Ontario this afternoon,” the watch read.
“Heavy downpours and wind gusts of 70 to 90 km/h are the main threats. A tornado is also possible.”
This story will be updated.