Two things that seem to counter each other:
Warm temperatures can soften your suspension... which makes it a tad more efficient, but more likely than not, not enough to notice.
I've noticed that Butyl rubber speakers seem more susceptible, where foam ones don't seem to be affected much at all, typically. But realistically, this SHOULD be more of a function of suspension compliance - and it's the SPIDER that really dictates that - so IT'S epoxy is really the variable that's changing, I'm positive.
The voice coil is another animal - it's more efficient when it's cool, and gets less efficient when it warms up - if we're talking SPL competitor, anyway - it might be worth a few tenths of a dB.
For daily use, it's a non-issue - since the thing heats up nearly instantly and stays warm while in use.
Car audio stuff is built to take a lickin' in all sorts of temperatures - even in extremes like we get here in Buffalo, NY (winters in the sub-zero, summers reaching way into the 90's - car interiors into the 120's easy in the sun), the difference in performance is pretty subtle.
