A snow squall watch for London, Parkhill and eastern Middlesex County has been upgraded by Environment Canada to a snow squall warning.
The warning, which also covers Huron County, calls for squalls to continue through the region overnight until late Thursday morning.
Snowfall amounts of 15 centimetres per 12 hours are possible, the advisory said, and visibility may quickly be reduced to near zero at times due to heavy and blowing snow.
As of 10:20 p.m., the national weather agency said snow squall watches remained for Strathroy, Komoka, western Middlesex County, eastern Lambton County, and Perth County.
Forecasters are calling for a high of -3 C and flurries on Thursday along with a risk of morning snow squalls. The sun will come out Friday, but things will stay cool with a high of 2 C.
Things will warm up over the weekend. Environment Canada said Saturday and Sunday will see sun and highs of 11 C and 10 C, respectively.
The typical high for this time of the year is between -1.5 and -1.2 C.