Environment Canada has issued a heat warning for most of southern Ontario including Sarnia-Lambton.
Temperatures are expected to reach 31C or 88 F Sunday and near 32 C or 90 F on Monday with overnight lows near 21 C or 70 F, providing little relief from the heat.
The weather agency is forecasting humidex values of 36 C and 37 C for the next two days.
Temperatures will fall below heat warning criteria by the middle of this week.
Watch for the effects of heat illness; swelling, rash, cramps, fainting, heat exhaustion, heat stroke and the worsening of some health conditions. Drink plenty of water even before you feel thirsty and stay in a cool place.
Cooling centres are located across Lambton. Click here for the full list.