Environment Canada Meteorologist Geoff Coulson is warning Southwestern Ontario residents not to be fooled by the warm temperatures.
He says the region is in for a big cool down.
While temperatures are still expected to get up to 10 C (50 F) in Windsor, and 9 C (48 F) in London, a mass of cold air is expected to interrupt your dreams of coffee on the front porch on Christmas morning as temperatures fall on Tuesday afternoon.
A high of 8 C (46 F) early on during the day, will tumble to just 2 C (36 F) in the afternoon. Environment Canada says residents can even anticipate flurries later in the week.
"For Windsor and Chatham, it looks like more like just on and off flurries over the course of the coming days. No major weather systems" says Coulson. "But a bit of a different story for the London area. We're going to have northwest winds off Lake Huron, and that could generate some significant lake-effect snow activity."
It could be a shock for many who basked in 16 C (61 F) temperatures just last Tuesday. Coulson says by next Tuesday, our daytime high may struggle to reach -5 C (23 F).
Earlier weather models suggested December would continue to boast above average temperatures, but Coulson says there is a strong suggestion that will not materialize.
"Even our official weather forecast for the month of December isn't really agreeing with some of the other forecast centres and other information that I have seen," says Coulson. "Our model ended up indicating December will be warmer than normal... with this change in temperature... and some other guidance that we're getting from other sources, it certainly looks like December, overall, will likely end up being colder than normal."
Snow and rainfall totals this month are predicted to be around average.