Everyone loves a little fun in the sun, but when people linger in the sun’s rays a little too long, it can have harmful effects on their health, especially for seniors.

Heat-related illnesses, collectively known as hyperthermia, occur when the body overheats and does not have the sufficient means to cool itself down. According to the Centers for Disease Control and Prevention, the elderly are more prone to the sun’s harmful rays because they are more likely to have a chronic medical condition or take medication that inhibits normal body responses to heat.

“People who work in high heat develop a certain degree of tolerance. With the elderly, their ability to adapt to extreme temperatures is limited, and the body’s ability to maintain status quo is much more at risk,” says Kris Stapp, vice president of community and public health at Omaha’s Visiting Nurse Association.

Heat exhaustion is a mild form of heat stress. Continuous exposure to high temperatures, combined with high humidity and physical exertion, can lead to dehydration. If you develop heavy sweating, a pale complexion, muscle cramps, and a sense of tiredness, you may be suffering from heat exhaustion. If not controlled, heat exhaustion can escalate to heat stroke, which can cause permanent brain and organ damage.

Stapp stresses the importance of taking into account the timing of outdoor activities, especially strenuous ones such as gardening or walking. Older folks may need to adapt their outdoor plans in times of extreme heat.

“What is dangerous about any heat-related illness is, it comes on so subtly that people don’t realize it’s happening until the symptoms really set in,” Stapp says. “When people get to the point where they are confused, it can lead to unconsciousness.”

To combat heat stress, the CDC advises drinking plenty of non-alcoholic beverages. Make sure to get plenty of rest and try to stay in air-conditioned environments during the heat of the day. Also, make sure to wear lightweight clothing if venturing outdoors.

“Be smart,” Stapp says. “It’s about turning all this information around, and not only knowing the warning signs, but also how to prevent it from happening.”