The heat is on for Arizona – specifically the Phoenix area – and it’s more than just an annoyance.

“It’s particularly dangerous for folks that either have outdoor occupations or that do outdoor work or even are exercising in the heat of the day, if they haven’t ‘cameled’ up with water before hand,” said Will Humble, MPH, director of the Division of Health Policy and Program Evaluation the University of Arizona’s Health Sciences Center.

The National Weather Service has issued an excessive heat watch for Arizona and Southern California that begins Tuesday and runs through the rest of the week. Temperatures in the Phoenix area are expected to top 110 this week.

Humble notes that heat is the No. 1 weather-related killer in Arizona and the United States, more than tornadoes, hurricanes, floods and wildfires combined.

“It’s hard to take a picture of heat so it gets less attention than things like floods, lightning, hurricanes and tropical storms,” said Humble, former director of the Arizona Department of Health Services. “The Arizona heat is a lot more than a nuisance – it’s dangerous and lethal.”

Experts remind everyone to stay hydrated, wearing light-colored clothing and keeping your head cooler with a hat. Symptoms of dehydration to watch for include headache, thirst and muscle cramps.