how does 40C in UK compared to 40c in the tropics? is it heat directly from the sun? Or is the atmosphere hot? or does the ground radiate heat? these three different types of 40C have different mitigation strategies but will be given the same number (40C) by weather report sources. All heat is not the same. humid 40C is completely different from dry 40C. Each of these various types of heat will have different effects on our health and efficiency and have different strategies to mitigate it.