Sarnia is soaking up the sunshine on Wednesday, August 5, 2026, with temperatures climbing to around 30°C, but residents should enjoy it while it lasts because rain and thunderstorms are on the way. Environment Canada says conditions are hot and sunny today, with a Humidex making it feel closer to 34, and the UV index reaching very high levels. Things start to change Thursday with a 60 percent chance of showers and a risk of thunderstorms.
At the Sarnia Chris Hadfield Airport, the temperature hit 29.2°C by late afternoon under clear skies. The Weather Network pegged the high at 30°C, with a feels-like reading of 33. The UV index peaked at 8, which is considered very high, so anyone spending time outside is reminded to wear sunscreen and protective clothing.
The heat will stick around Thursday, with a forecast high of 28°C, but the Humidex is expected to climb to a sticky 37. Fog patches may linger into the morning before clouds roll in with that risk of thunderstorms. No weather alerts are currently active for the area, but the shift in conditions means people with outdoor plans later in the week should keep an eye on the forecast.
Thunderstorms are not unusual for this time of year in Lambton County. According to the County of Lambton, these storms typically brew in warm, humid air between May and September and usually last an hour or less. Even so, they can bring dangerous lightning, so the county urges everyone to head indoors if thunder roars.
Looking further ahead, Sunday is forecast to bring back sunshine with a high of 28°C, offering a brief break before another system arrives Monday and brings a 60 percent chance of showers. For now, the message is simple: get outside and enjoy the heat today, but be ready for the change starting tomorrow.
