We do here in Nor Cal, where it get down to below zero during the Winter. No fleas here.
We also get down to zero here in Chicago; our last dog had fleas multiple times. Our previous before her never had them, and our current is on Bravecto.
I’m over fleas. It was awful.
I should have been more specific, Southern California. I recall being warned about the plague in squirrels since the late 70s.