Oshawa, Ontario residents can expect a mild and mostly settled week of weather, with daytime highs near seasonal norms and no alerts in effect, according to Environment Canada.
As of 1:00 PM EDT on Monday, September 21, 2026, conditions at Oshawa Executive Airport were mainly sunny with a temperature of 14.2°C. Forecasts call for a mix of sun and cloud through the week, with highs ranging from 17°C to 21°C, close to the normal high of 18°C for this time of year.
Northeast winds of 20 km/h gusting to 40 km/h are expected on Monday and Tuesday. Residents planning outdoor activities should be aware of the gusty conditions, but no significant weather is anticipated.
Friday and Saturday are forecast to reach 20°C, with Sunday possibly hitting 21°C. Overnight lows through the week are expected to range from about 4°C to 11°C, with Thursday night dipping to 4°C. The official forecast does not mention any precipitation or showers for Wednesday, with Wednesday night expected to be cloudy with a low of 11°C.
The stable pattern is influenced by developing El Niño conditions, which historically bring average to slightly above average temperatures for southern Ontario in September.
