The tires are designed to handle the variances in tire pressure caused by temperature.
Look at it this way....suppose you are in a hot location and the outside temps is 100 degrees. You are carrying the maximum load so you inflate the tires to the sidewall max. Obviously once you hit the road, the tire temperature will increase, which will increase the tire pressure even more. Even tho this is above the max on the sidewall, it is not a problem and is still well within the tire design specs.
As you know, under-inflation is what kills most tires.
