A severe thunderstorm watch is in effect for the region, with potentially dangerous weather expected to develop this afternoon and continue into the evening.
Conditions are favourable for thunderstorms capable of producing damaging winds, large hail and torrential rainfall.
Wind gusts could exceed 110 kilometres per hour, while hail ranging from quarter to ping-pong-ball size is possible.
Some areas could also receive up to 50 millimetres of rain during heavy downpours.
There is also a risk of a tornado.
Thunderstorms are expected to develop during the mid-to-late afternoon along and ahead of an advancing cold front.
Forecasters say some uncertainty remains because lingering cloud cover could limit the amount of instability that develops. However, current observations and weather models indicate enough instability is likely to develop to create a significant severe-weather threat.
The primary concerns are potentially damaging winds, large hail and torrential rainfall, although conditions could also allow some thunderstorms to produce a tornado.
The weather could result in power outages and significant damage to trees, buildings and other property. Large hail also carries a risk of injury and damage.
Residents are being urged to be prepared and move indoors if threatening weather approaches.
Anyone caught outside should seek sturdy shelter and protect themselves from hail and flying debris. Emergency Management Ontario recommends taking cover immediately when threatening weather approaches, preferably in a basement or interior room away from windows.
A severe thunderstorm watch means conditions are favourable for storms capable of producing damaging wind, hail or heavy rainfall.
