The first day of summer will arrive today once the clock hits 6:34pm.

Environment Canada says the most significant heat episode of the year so far will be today with temperatures in the low to mid-thirties.

Later today, an approaching cold front will arrive with scattered showers and thunderstorms, followed by cooler temperatures tonight.

Officials say everyone is at risk from the heat.

They urge residents to drink plenty of water, and keep cool by dressing for the weather.