In a Q&A, a Yale emergency medicine specialist explains common heat illnesses—and how to stay safe this summer.

David Della-Giustina knows what it’s like to be in extreme heat.

A retired US Army colonel with more than 29 years of service, he did combat tours in Afghanistan and Iraq, where he often endured extreme temperatures while serving as a physician.

“We train a lot for being in the heat as well as the cold and how to deal with it, as well as how to manage casualties and how to protect ourselves,” says Della-Giustina, who is now a professor of emergency medicine at Yale School of Medicine, where he is also vice chair for education of emergency medicine and program director of the Wilderness Medicine Fellowship.

But you don’t have to be deployed overseas to encounter extreme heat. Extreme temperatures have become increasingly common in the US, for instance, especially during the summer, and are expected to become even more frequent and intense in the coming decades due to climate change.

As the temperatures rise, so does the risk to people’s health, posing a host of dangers, from heat exhaustion to heat stroke.

Here, Della-Giustina discusses common heat illnesses, when a person should seek medical help, and how to reduce risk: