Beach trips, cookouts and other outdoor activities are in full swing as summer arrives and the first widespread heat wave of 2025 hits the U.S. For many people, summer is their favorite time of year.

As extreme heat grips much of the United States, it's vital to take steps to stay safe. Always check the heat index—not just the air temperature—as it accounts for humidity and gives a clearer sense of how hot it feels.

The National Weather Service issued an extreme heat warning through Monday. Here's what to know about heat conditions this week.

Arizona’s extreme heat isn’t letting up, and daytime highs in the Valley will range from 110 to 116 degrees every day through Friday.

Things will stay hot on Wednesday in Phoenix, as our high will be about 112°F. Highs will stay over 110 degrees for the rest of the work week. By Sunday, we'll see extreme heat relief with a high in the low-100s.