Heat is always the enemy. The amps in the subs don't tend to get very hot but if the amp plate is left in direct sun in the summer it would double the problem. Keeping the amps shaded would be a good idea. Only 2 to 8% of the amp's output is converted to heat, so its cooling requirements are low. If it does get hot enough it will reduce output to prevent overheating. If the heat continues to rise after the level reduction, it will shut down. Fan cooling can be added if that becomes a problem. The air movement generated through the ports helps to cool the amp so I don't expect running it harder will cause it to overheat more. So far we haven't been able to get the amps above barely warm.

Ambient heat will affect how well the drivers cool but there's not much to be done about it, other than turning the system down, that will reduce the operating temperature. Amps run 90 to 98% efficient, meaning 2 to 10 percent of the energy is waste heat. Woofers run 1 to 4% efficient, meaning 96 to 99% of the energy going into them is converted to heat, the remainder into sound. Heat is the enemy, more so in the voice coils than in the amps. We have to limit the inbound power to prevent excess heat buildup but ambient temperature will change how long they can be run at maximum output. If the limiters are set for high-temperature conditions, then max levels in cooler temps would be compromised. Normally we expect things to be pretty hot so even in the desert heat, you should be OK, just remember that you do have control over the level.

Thinking of the volume knob as a 4 percent sound a 96 percent heat knob would be informative.