Emergency room doctors are urging people this summer to be aware of signs of heat exhaustion or heat stroke.

"You start have confusion, delirium as we call it, as well as loss of consciousness and more severe brain injury as a result of the effects of heat," says Dr. Ayan Sen, an Emergency Medicine Physician at the Mayo Clinic.

Heat-related illnesses can also impact the heart, lungs and kidneys.

"It's almost an inflammation that gets created. There's a destruction of proteins, the membranes of the cells, and that leads to cell death," says Dr. Sen.

Doctors say children under 4 years old, seniors, pregnant people and those with underlying health conditions are most vulnerable to the heat.

To keep your body safe, they recommend wearing lightweight, light-colored and loose-fitting clothes.

It's also better to work out earlier in the day before it gets too hot.

Doctors also say to avoid beverages with large amounts of sugar which can lead to dehydration. Drinking water not only replaces the liquid being sweated out, but brings down body temperatures.

MORE: Safety tips: Know the signs of heat exhaustion and heat stroke