Some heavy thunderstorms developed across the region Wednesday afternoon in advance of a cold front.
Most of the activity missed Sarnia-city but some storm cells rumbled through central and north Lambton County.
Environment Canada's thunderstorm watch was elevated to a warning for London-Middlesex.
The weather agency said the greatest threat in the storms was the potential for strong wind gusts up to 100 km/h, hail and locally heavy rain.
The watch for Sarnia-Lambton ended before 5pm.
It'll be considerably cooler Thursday with northerly winds and a high of 22 C (72 F).