A dangerous heat wave is blanketing much of the central and eastern United States this week, sending temperatures into the triple digits and affecting nearly a hundred million Americans.

While many people have heard about the risk of heat stroke, experts say that extreme heat can affect almost every part of your body. Here’s what to know, and how to stay safe.

1. Watch Out for Brain Fog

Heat can slow down the brain, reducing reaction time, attention and memory, said Dr. Neha Raukar, an emergency medicine physician at the Mayo Clinic. That can mean performing worse on tests as well as having trouble concentrating and being productive at work. The heat can even make people more irritable and aggressive; researchers have observed that more road rage incidents and violent crimes occur when temperatures rise.

While the reasons are not entirely clear, experts believe that your brain might be more focused on staying cool than thinking clearly.

2. Make a Plan to Stay Cool

Beating the heat can be an all-day challenge. If you don’t have air-conditioning, it’s smart to take steps like closing the shades, immersing your feet in cold water and wrapping a damp towel with crushed ice around your neck, said Kristie Ebi, a climate epidemiologist at the University of Washington. Fans can also be helpful, but make sure you leave your windows open so that you don’t turn your house into a convection oven, she added.