Severe Thunderstorm Risk Expands Across Ontario Wednesday

A large portion of Ontario is facing the potential for severe thunderstorms Wednesday afternoon and evening, with damaging winds, large hail, tornadoes and torrential rainfall all possible.

The greatest risk is expected across southwestern and central Ontario and the Golden Horseshoe, where the thunderstorm environment has the potential to be among the strongest seen in the area this year.

The strongest storms are expected during the afternoon and early evening.

Storms in the highest-risk area could produce damaging wind gusts, large hail and tornadoes, along with intense rainfall. Rainfall totals could reach 50 millimetres, with locally up to 30 millimetres falling in an hour.

The storms could toss loose objects, damage weak structures, break or uproot trees and cause property damage. Dented vehicles and injuries are also possible, while power outages are considered likely in the highest-risk area.

Heavy rainfall could result in flash flooding and significant water pooling on roads.

A second area covering portions of central, eastern and extreme southwestern Ontario is also at risk for severe thunderstorms Wednesday afternoon and evening.

The same hazards, including damaging winds, large hail, tornadoes and torrential downpours, are possible in this area, although confidence is currently lower than in the highest-risk zone.

Rainfall totals could reach 50 millimetres, with locally up to 30 millimetres in an hour. Downed trees, property damage, injuries, localized flooding and power outages are possible.

Farther east, portions of eastern and central Ontario face a lower but still notable risk for thunderstorms.

Storms in this area could produce strong winds and hail, while heavy rainfall could cause flash flooding and water pooling on roads. Rainfall totals could reach 40 millimetres, with locally up to 20 millimetres in an hour.

The greatest threat for damaging winds and large hail currently appears to be southwest of this area, although conditions will continue to be monitored for a potential upgrade.