A late-season frost advisory has been issued for northwestern Ontario as the mercury is set to hover near the freezing mark overnight Friday.

Environment Canada says patchy frost is expected tonight into Saturday morning.

Resident should cover up plants, especially those in frost-prone areas.

The overnight low for Kenora, Dryden, and Vermilion is plus 1, while the Sioux Lookout area will dip down to minus 1, before temperatures return to normal towards the end of the May long weekend.