A severe thunderstorm warning has now been issued for some parts of Niagara.
North Niagara including Grimsby, and St.Catharines are under the warning while the rest of the region remains under a watch.
Envirnoment Canada says people in north Niagara should be on the lookout for adverse weather conditions and take necessary safety precautions.
The main threats are heavy rain and strong wind gusts.
Strong wind gusts can toss loose objects, damage weak buildings, break branches off trees and overturn large vehicles. Hail is also possible.
Heavy downpours can cause flash floods and water pooling on roads.