Winter will arrive with a bang in southwestern Ontario.
Environment Canada Meteorologist Gerald Cheng said the season will start with a low pressure system moving in by the end of the week.
"Thursday we'll be dealing with a bit of snow and rain and then Friday, temperatures are going to drop like a rock and there will be snow," said Cheng. "And, it will be combined with some very strong winds Friday into Saturday, so this is going to be a very eventful week."
On Monday, the national weather agency issued a special weather statement for southern Ontario, including Sarnia-Lambton, Chatham-Kent, London-Middlesex, Windsor-Essex, Grey-Bruce, and Huron-Perth. However, the advisory was upgraded to a winter storm watch late Wednesday night.
Cheng said while there is high confidence in a high impact winter storm, the details regarding wind speeds, precipitation types and amounts remain uncertain at this time.
"Things are going to definitely change, because the system is on its way, it's still forming right now," he said. "First ones in line will be northern Ontario late Wednesday and eventually by Thursday, we'll start to feel the effects of the system, but things really get going Friday into Saturday with snow and wind."
Motorists are advised that travel conditions may become dangerous and power outages are also possible.
Cheng said because of the system, it's very likely most regions in southwestern Ontario will have a white Christmas.
"Because we will have a system coming through and we will have cold temperatures, basically Friday into Saturday and into Sunday, so if we have snow and if the temperatures stay cold, then we will likely have a white Christmas."
Winter officially arrives at 4:48 p.m. on Wednesday.
Cheng said there's some indication we will see above seasonal temperatures to start.
"But you know the signal is not really strong, so we don't really have high confidence that it's going to be above normal," he said. "So that's something to keep in mind because we know that there will be big fluctuations in the winter time, just like we will see this week and we can expect that even for January into February."
Wednesday will be the shortest day of the year with the fewest hours of daylight.