When you gotta' play, you gotta' play!
Here in Chicago, low 40's to high 30's if the wind lies down. A little bit of Sun doesn't hurt. I've already played in low 40's this fall. It sucked, but not as much as not playing.
I have a buddy who's crazy about platform(?) tennis. They'll play while sporting snotcycles.
"I was one of the best off my croop of buddies, yet I never happened to be the first to cover a chic after a nightly rodeo..." - the kikster