Saturday is the first day of summer, and that has health officials warning people about staying safe in the sun. 

Henry Varela, a health department public information officer, says this is the time of year when it's easy to fall victim to heat exhaustion, which can cause serious health problems. 

He says those at greatest risk of heat-related illness are seniors and children.

"Children's body temperatures rise at three to five times that of an adult. Therefore, when it comes to children, they're probably more at risk than anybody else," Varela said. 

Varela stresses that leaving a child in a hot car even for a short time can be dangerous and have negative health consequences.

The CDC reports more than 650 people a year die from heat-related causes.