Durham Region residents should prepare for unsettled weather on Tuesday, July 21, as thunderstorms capable of producing heavy rain, strong wind gusts and hail move across southern Ontario.
The Durham thunderstorm risk forms part of a broader Environment Canada outlook covering most of southern Ontario, including the Greater Toronto Area. The provincial outlook indicates that stronger storms in this zone could produce wind gusts approaching 80 km/h, rainfall totals of up to 40 millimetres and localized downpours reaching approximately 30 millimetres in one hour. Hail is also possible.
Environment Canada’s local Oshawa forecast is less severe but still calls for mainly cloudy conditions, showers beginning early Tuesday and a risk of a thunderstorm. Southwest winds are expected to reach 30 km/h with gusts up to 50 km/h. The daytime high is forecast to reach 24 C, with a humidex near 31.
Durham Thunderstorm Risk Covers the Region
The weather system could affect Oshawa, Whitby, Ajax, Pickering, Clarington, Uxbridge, Scugog and Brock. Conditions may vary considerably across Durham because thunderstorms can develop quickly and produce intense weather in one community while nearby areas receive lighter rain.
The most significant hazards are expected to be strong winds and heavy rainfall. Powerful gusts can break tree branches, bring down weakened trees and damage unsecured outdoor objects. Falling branches may also interrupt electricity service or create hazards on local roads and trails. Environment Canada’s weather-impact guidance notes that thunderstorms can cause difficult driving conditions, utility outages, tree damage and localized flooding.
Heavy downpours can reduce visibility for motorists and cause water to collect on streets, parking lots and low-lying areas. Residents should not attempt to drive through a flooded section of road because the depth of the water and the condition of the pavement beneath it may be impossible to determine.
Hail remains another possibility, although it is not expected in every community. Vehicles, gardens and outdoor equipment may be damaged if a stronger storm develops over the region.
How Durham Residents Can Prepare
Residents should secure patio furniture, recycling containers, umbrellas and other lightweight outdoor objects before the storms arrive. Phones and portable power banks should also be charged in case electricity service is interrupted.
People planning outdoor work, sports, camps or community events should monitor the forecast and be prepared to move indoors. Environment Canada advises people who hear thunder to seek shelter immediately inside a sturdy enclosed building or a hard-topped vehicle. People should remain sheltered for 30 minutes after the final sound of thunder.
Drivers should slow down during heavy rain, leave additional space between vehicles and avoid sudden braking. Anyone encountering a downed power line should stay at least 10 metres away and notify the appropriate utility or emergency service.
Pet owners should bring animals indoors before thunderstorms arrive. Households with basements should also check sump pumps, downspouts and drainage systems if their properties are vulnerable to water entry.
Outlook Could Change Before Tuesday
As of late Monday morning, no weather warning was in effect for Oshawa. The information available was a thunderstorm outlook and local forecast rather than a severe thunderstorm warning. Watches or warnings could be issued later if forecasters become more confident about the storms’ timing and intensity.
The Durham thunderstorm risk depends partly on when storms develop and how much unstable air becomes available. Some locations may receive only showers, while isolated communities could experience stronger winds, hail or torrential rainfall.
Residents should monitor Environment Canada forecasts, weather radar and alert notifications throughout Tuesday. Conditions can change quickly, and any newly issued official warning should take priority over earlier forecasts.
