The last full day of summer Friday will be warm, humid and very windy.
Environment Canada issued a special weather statement for Sarnia-Lambton Thursday afternoon.
The weather agency said strong west-southwesterly winds will develop in advance of a cold front for Saturday's official start of fall.
Wind gusts of 70 kilometres per hour to 80 kilometres per hour are expected Friday afternoon and evening.
Higher winds are possible in thunderstorms. A severe thunderstorm watch was issued for Sarnia-Lambton Friday morning. Environment Canada says conditions are favourable for the development of dangerous thunderstorms that could produce damaging winds gusts, large hail and heavy rain.
Autumn officially arrives at 9:54 p.m. Saturday and it will feel like fall.
It'll turn considerably cooler for the weekend with Saturday's high in Sarnia reaching only 18 C, 64 F.
Environment Canada meteorologist Peter Kimbell said September has been warmer than usual so far.
"The mean temperature in the month of September would be 16 C and we've had so far a mean temperature of about three degrees warmer than that," said Kimbell. "That, of course, has been biased by very warm temperatures the last couple weeks or so, but that's not going to continue, and going into October the mean temperature is about ten."
The Weather Network's autumn outlook calls for temperatures to be near or just below seasonal in October, and just above what's normally expected in November.
-With files from Josh Boyce and Adelle Loiselle