Even if LED or even CFL bulbs create far less waste heat than a conventional lightbulb, they react far more adversely to the heating resulting from ANY waste heat. A lightbulb won't care if it is in an ambient temperature of 500°F, actually it will run more efficiently - anything with electronics in it is hard to make in a way that it will survive long in more than 220°F/105°C (highest commonly used specification for plastics, capacitors and wiring. And that is industrial grade parts, 160°F/70°C is more common), and LEDs are a) even more sensitive, b) dissipate their own waste heat in a very very small space so they depend on ambient temperature being low for that small space not to get far too hot, c) drastically change their color profile with increasing temperature (not so important, though, with the flourescence-based designs common in white LED lamps), and d) LOSE efficience with higher temperature - you can destroy certain laser diodes (same light-generating physics) by cooling them too far down if they are driven from a constant current, their optical output gets too strong because efficiency rises with cooling. Also, another effect works on top of that, to the same result: A hotter LED will draw LESS energy from a constant current driver because the junction voltage will be lower.