Environment Canada has issued a winter storm watch for Waterloo Region and surrounding areas, with freezing rain and ice pellets expected Thursday.

The weather agency says there is a risk of a thunderstorm Tuesday night.

Rain is expected to continue into Wednesday, with a total of 10 to 20 millimetres of accumulation. Ice pellets and freezing rain are then expected Thursday, will be persistent throughout the night and may be "heavy at times," said Environment Canada.

"A series of low pressure systems will give periods of rain into Wednesday night," the weather agency said in a statement Tuesday afternoon.

"On Thursday, a stronger low will arrive from the southwest and combine with a cooler air mass from the north."

Environment Canada warns of poor travel conditions and possible power outages.

Conditions are expected to improve by Friday.