Texas officials say power outages could last weeks in parts of Houston after thunderstorms with hurricane-force winds tore through the city and killed at least four people.

The storm knocked out electricity to nearly 1 million homes and businesses in the region as temperatures hover around 90 degrees Fahrenheit (32.2 Celsius). Multiple transmission towers were downed, and thousands of utility workers have headed to the area, said Harris County Judge Lina Hidalgo, the county’s top elected official.

What should you do to stay cool and safe at home when summer power outages prevent you from using fans and air conditioners? Emergency response and medical experts share their tips.

HOW TO STAY COOL

To avoid overheating, it’s key to stay hydrated. If your home is without water during a power outage, be sure to stock up on bottled water.

It’s also important to refrain from exertion, if possible. Avoid the sun, especially during the hottest part of the day, and stay in the shade when outside.