There's a severe thunderstorm watch in effect this morning.
Storms are expected at various times over the next two days.
Geoff Coulson, a meteorologist with Environment Canada, says we've had relatively few severe storms in southwestern Ontario so far this season.
But across Ontario, seven tornadoes have been reported.
Coulson says in an average year, Ontario sees a dozen tornadoes.
"We also know that it's been almost 30 years since the devastating [F4]tornadoes that occurred in Barrie and Grand Valley. A lot of our activity, especially this year again has been at the lower end of the damage scale, but as the years have gone by, every year that possibility of seeing something more significant occurring down in the extreme southwest is there with us," Coulson said.
The weather system moving in this week could prompt more serious storms.
Coulson says to be aware of any watches or warnings come from Environment Canada.
He says quick moving storms can make it from your horizon point to you in a matter of minutes.
"On average, we're providing somewhere between 10 and 15 minutes advance notice for many of these tornado events," Coulson said. "Some of them may have little to no notice and it's all derived from the fact that as to how unpredictable they can be."
Coulson recommends to seek shelter if you see the southwest skies forming dark clouds, see lightning or hear thunder.