Monday was the hottest September 25th on record in the Kitchener area.
By late afternoon the temperature had risen to at least 31.4 C at the airport, narrowly surpassing the previous record of 31.2 C, set on Sept 25 2007.
According to Environment Canada the unseasonably hot temperatures are due to a high pressure area to the south, pumping warm and humid air northward.
'Incredibly Rare Event'
"This is an incredibly rare event," said Geoff Coulson, warning preparedness meteorologist with Environment Canada. "Certainly, we get warm weather in late September and early October, but I don't think we've ever seen ... this much warm air, this late in the year, going on for the number of days that it has."
Heat records have been kept in Kitchener since 1915, and at the airport since 1970.
Temperatures this September have broken records throughout the province.
"Records started being broken across Southern Ontario last week," said Coulson. "We had records broken in a number of locations over the weekend, records breaking today in a number of areas, and it looks like the way things are shaping up, records could be tumbling Tuesday and Wednesday as well."
A cold front is expected to return temperatures to more seasonable norms by Thursday. Wednesday's high is forecast to reach 25 C; Thursday's high will be 19.