Ambient heat is a new feature of version 50. It can also be called "air temperature."
As it's name suggests, it is heat currents that travel along air currents. To view Ambient Heat, turn it on in the menu and switch to heat display (6)
As you can see, the entire field of play is surrounded by heat, the normal 22C. If you were to place a very cold object (say, a GOL cooler)
The air temperature would begin to change. Like pressure, it is blocked by walls. Therefore, it is completely possible to combine the Decor layer and Ambient Heat to create a fully stocked fridge!
Ambient heat cannot be directly influenced by the player in the fact that the heat/cool tool cannot affect the ambient temperature. Also the ambient temperature cannot be seen with the HUD as the pressure can its intensity is only shown through the color changes.