TORONTO - Environment Canada is warning residents of southern Ontario and southern Quebec to brace for wet and sloppy conditions which could lead to a flash freeze overnight.

The weather agency says a low pressure system has spread a mix of rain and wet snow across southern Ontario with more snow expected overnight as the temperature drops.

A heavy snowfall warning has been issued for parts of eastern Ontario -- including Ottawa, Cornwall and Brockville --with 10 to 15 centimetres forecast in some areas.

Meanwhile, an Arctic cold front will cross southern and eastern Ontario tonight, bringing much colder air and temperatures below freezing.

Travellers are being warned the sharp drop in temperature could lead to hazardous conditions on roads and sidewalks.

In Quebec, Environment Canada is warning of heavy snow and strong winds in several parts of central and eastern Quebec.

Montreal and Laval could receive up to 10 cm of snow and close to 20 mm of rain.

North of the St Lawrence river, only snow is expected with a chance of freezing rain.

A special weather warning that was issued for parts of northern Ontario, including Sault Ste. Marie, Sudbury and North Bay, has since ended.

Air Canada and West Jet are warning customers to expect flights to be delayed due to snow in Ottawa, Toronto, Montreal and Quebec City.

Porter Airlines has issued similar warnings and has added Windsor, Ont., to the list of cities with potential flight delays.

There have been a number of delays and some cancellations at airports in Toronto, Ottawa and Montreal.