Ajax will see a hot and sunny start to the week before unsettled weather moves in, according to Environment Canada. Monday, June 8, 2026 brings clear skies and a high of 26°C, with a humidex of 28 and a very high UV index of 9. No weather alerts are in effect, but residents should take care in the sun.
The UV index of 9 falls in the very high category, meaning people should limit sun exposure especially between 11 a.m. and 3 p.m. Environment Canada recommends wearing UV protection sunglasses, staying in the shade, and reapplying sunscreen every two hours. Unprotected skin can burn quickly on clear, sunny days like Monday. Southern Ontario, including Ajax and Durham Region, experiences Canada’s highest UV index values during spring and summer.
On Tuesday, June 9, the weather begins to shift. There is a 40% chance of afternoon showers and a risk of a thunderstorm, with a high of 29°C and a humidex of 35. Overnight, the chance of showers increases to 60%. The unsettled pattern continues through the week, with a mix of sun and cloud and a 40% chance of showers on Thursday, June 11, when the high reaches 30°C. These temperatures are well above the early June norm of 23°C for Ajax.
Ajax sits along the north shore of Lake Ontario, where hot and sunny conditions can cause increasing ground-level ozone concentrations. The current weather data is recorded at the Oshawa Executive Airport weather station. The Weather Network reports current conditions at 22°C with no active alerts.
Forecasters advise people to stay hydrated and adjust outdoor plans as showers arrive. Durham Region maintains cooling stations, outdoor pools, and splash pads to help residents beat the heat during hot weather.
