How a heatwave can affect your brain and mood

Dresser says the evidence suggests that heat can influence us in sometimes indiscernible ways. "All of these [studies] seem to point to a reduced ability to think clearly and quickly and efficiently when the body is too hot," he says.

There's also research to suggest that heat can make you moodier or irritated, in part, perhaps, by raising cortisol levels, and inducing a stress response.