Heat is one of the strategic considerations in every engagement. If a 'Mech's heat exceeds the overheat threshold at the end of a turn, it will take internal structure damage. The threshold is 50% + 5% per point of Guts of the 'Mech's heat capacity. Reaching the end of the heat capacity will cause a shutdown and require a turn to reactivate the mech a shutdown is not desirable for your own units, as it gives the enemy a free called shot - of course, it also works in reverse: Overheating enemy mechs is an effective way to get free pot shots at their vulnerable bits.
You can see heat for your own mechs in the user interface - a bar that fills gradually with red, and flashes yellow when you are likely to exceed the heat threshold. In addition, heat affects the mech animations in game (for both your and your opponent's mechs). A mech approaching the heat threshold will appear to be surrounded in heat haze, and look a bit blurry. An overheated mech that is taking damage will glow red-hot.
- Firing weapons. Generally energy weapons cause the most heat and ballistic weapons the least.
- Jumping causes 7.5 heat per jump jet
- Being hit by a Flamer. (Multiple flamer hits can be very irritating, and degrade the target's combat capability much more than the damage amount suggests).
Heat is removed by heat sinks. Every 'Mech gets 10 heat sinks included as part of their reactor. 'Mechs may mount additional heat sinks, which remove 3 heat per turn each . Standing in water doubles the effectiveness of heat sinks, and the biome also has a significant impact on heat sinking.
Exchangers reduce the amount of heat generated when firing weapons by a fixed amount and are not affected by temperature of the biome or terrain.
Heat Banks increase the overheating threshold and the total heat amount to cause shutdown.