If you are heading up the highway be aware a severe thunderstorm warning is in effect for an area from Hamilton to Waterloo.
The weather office says conditions are favourable for the development of dangerous thunderstorms that may be capable of producing damaging wind gusts and heavy rain.
Niagara is not included in the weather warning.
A special marine warning is also in effect for Western Lake Ontario warning of thunderstorms over Southwestern Ontario tracking eastward at 40 knots.
The weather office says the thunderstorms are capable of producing wind gusts to 25 knots, along with heavy downpours and frequent lightning.