THUNDER BAY — City residents who dressed for abnormally cool weather on Friday found themselves shedding their jackets and sweaters just a few hours later.
An abrupt swing in the temperature caught people off guard after the direction of the wind shifted in the afternoon.
At 2:00 p.m. Environment Canada reported it was only 9 C at its monitoring station at Thunder Bay Airport, or about 7 degrees cooler than the typical maximum for May 9.
By 6:00 p.m. the temperature had rocketed upwards by 18 degrees, reaching 27 C.
"It's certainly a very impressive jump in temperature in just the span of four hours," said meteorologist Jeff Coulson.
He said a change in wind direction was chiefly responsible for the rapid spike.
"It all comes down to the very cool temperatures remaining in Lake Superior. The water surface is running between 3 and 5 degrees. So when we bring a warmer air mass over that cold water, it tends to cool the temperature."
Coulson explained that up until the early afternoon on Friday, the wind was coming off the lake.
"Then it started to weaken and gradually shift over to the north and the northwest, and that tapped into a much warmer mass of air that was not being modified by Lake Superior."
He called the ensuing temperature swing "very significant" but didn't have immediate access to data for determining whether it established a record for the Thunder Bay area.
