what a bunch of sissies.
the low limit is about 10F... yes, F as in F@#$ the cold.
wear some thermals and some gloves, you are good to go.... the first 10min maybe hell, then it's all happiness thereafter.
ball bounce does become an issue, make sure you don't let them lay on the court... put them in pants pocket so the body heat keep them bouncy.
sounds crazy? you see plenty of crazy people jogging in 10F, why not tennis.
in PA, this should allow playing thru the winter, as long as no snow..... rain is non-issue either, I have an all-nylon racket just for hitting them things when it's wet... you should see, the ball goes like a flying sprinkler head when it's soaked