Yes indeed Chuck, elevated battery temperature should be a real concern. One battery manufacturer stated that for every 15F degrees above 75F, battery lifetime is cut in HALF. Considering this, it's easy to see why vehicle batteries don't last long.
Here in the tropics, it's very much a concern of mine and is why I elect to keep them in the air conditioned house where it's a constant 80F. I certainly couldn't afford to replace them twice as often as I do.
Obviously, I don't have an issue at the other end of the scale, so my problem is relatively simple compared to a more temperate climate where you have to deal with extremes at both ends.
I don't have any pat answers for your situation, but I would suggest that you consider higher temperatures more of a threat to battery longevity than the other end.