Yes, heat can affect your brain and mood. Here's why (npr.org)

If you're feeling a bit brain-fogged these days, you might not be wrong to blame it on the heat.

Other studies have found an effect from heat on office workers and on standardized test score performance, says Caleb Dresser, an emergency medicine physician who also serves as the director of health care solutions at the Harvard Chan Center for Climate, Health and Global Environment.

One of these studies showed that productivity in the workplace is highest when the air temperature is about 72 degrees, and productivity starts to drop off in the mid-70s. Another shows that for high school students, taking a standardized test on a hot day is linked to poorer performance.

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.

But given the extreme heat waves that are becoming more common, there's increasing interest in better understanding the mechanisms by which heat may exacerbate or set off mood and anxiety-related problems. Dresser points to a study published in JAMA Psychiatry in 2022 that found hospital ER visits for mental health conditions rise during extremely hot days.