Mark, I got lots of input on this when I moved to Florida. In general,here is what I got:
1. Chance for moisture buildup inside tubes because of high humidity in FL 2. Rubber hoods and tires will probably age faster and tubular glue and saddle glue may come undone. 3. Paint will not be harmed. 4. Grease may run to bottom of bb & hubs.
The only observed problem has been that the little pieces of tape that secure the handlebar tape have come unglued on all of my bikes.
I have 6 of my bikes in the attic. The temp has been 115-120 several times this summer inside the attic. But, the temp is routinely 95 inside the garage where I have the other bikes stored. So, short of bringing them inside the house, I'm not going to worry about it.
Lou Deeter, Orlando FL