We’ve all had days where the heat makes us a little cranky. It’s too hot to move and all you want to do is hop in a cold shower. But the impacts of heat can go much deeper than just your mood. Susan Clayton, PhD, a professor of psychology and environmental studies and psychology department chair at the College of Wooster, explains that heat can have a huge impact on your mental health.

“There are significant increases in mental health problems associated with high temperatures and that includes psychiatric hospitalizations and suicide levels—really serious, serious increases,” says Dr. Clayton. “And there’s a lot of evidence that people’s mood is not as good. Their ratings of happiness are lower. If you ask them about things designed to get sort of general well-being, those ratings are lower as in warmer temperatures.”

Dr. Clayton says science hasn’t fully figured out the strong relationship between heat and mental health.

“Some of the possible mechanisms are that we know that that heat can decrease social interactions,” says Dr. Clayton. “People are not as nice to each other, they tend to be more aggressive. So of course that might have an impact on your mental health if people are not being as nice to you.” Additionally, the physical impacts of heat like dehydration, confusion, and heat exhaustion can impact your mental health. “If you’re not feeling as well you might be crankier,” she says. “Also, heat can interfere with your sleep and lack of sleep can definitely lower your well-being level as well as kind of encourage mental health problems.”

Typically, research defines “too hot” as higher than average temperatures. Even in places that are naturally hotter people respond negatively when it’s hotter than usual.

“The effect of hot temperatures on suicide seems to be just as high in Mexico as it is in the U.S. despite the fact that average temperatures are higher in Mexico,” says Dr. Clayton. “There’s seems to be a maybe a certain degree of heat that you just don’t really adapt to.”

While spending days inside without an air conditioner during a heatwave will likely have a negative impact on your mental health, you can also feel the effects after an hour-long walk.

“There are some impacts that can set in pretty quickly depending on hot it is,” says Dr. Clayton. “You would expect the impacts to get worse as the heat lasts longer, but we don’t have very good data about that.”

Some people, like the elderly and those who are already experiencing mental health problems, may be more susceptible to the mental health impacts of heat. “Some of the medications you might take for mental health problems actually interfere with your ability to regulate your own body temperature,” says Dr. Clayton. Children may also be at a higher risk because their psychological systems for regulating temperature might not be fully developed. “This is why you have to yell at your children to come inside if it’s too cold.” And no matter how accustomed they are to it, people who work outside are more susceptible. There are physical limits to what your body can take,” says Dr. Clayton. “And so if you’re having to work outside during really hot and unpleasant conditions you’re going to be more vulnerable to those conditions.”

You’ll want to find ways to stay cool by staying hydrated and avoiding exercise outside when it’s too hot, for example. Because of the impacts of heat on health, some cities like New York have dedicated cooling centers for those without air conditioning. But Dr. Clayton says the work shouldn’t stop there.

“This is something cities need to be thinking about given that it’s going to get hotter and hotter. I was reading a piece about Phoenix, which is apparently the hottest city in the U.S., and they are thinking about not just cooling centers but designs that can reduce temperatures like just providing more green spaces because trees and foliage will tend to reduce the heat and providing more shade. That’s a longer-term solution.”