The Sarnia and District Humane Society says it has responded to about a dozen calls about animals left in hot cars the past couple of days.
Nicole King is an agent with the Ontario Society For The Prevention Of Cruelty to Animals. (OSPCA)
She says it's alarming that so many pet owners are not responsible.
"A car heats up like you wouldn't believe, even five to ten minutes could be fatal in these temperatures we are going to have today and tomorrow," says King.
A heat warning is expected to remain in effect today and Thursday with conditions becoming cooler Friday.
King says pet owners heading out during the day to make several stops should leave the animal at home.
Anyone who sees a pet potentially in distress in a hot vehicle should notify the local humane society, the OSPCA or police.