These scorching dog days of summer are a reminder of the danger of heat-related illnesses.

Heat exhaustion and heatstroke are the main medical problems that can affect anyone, but particularly afflict the very old and very young.

Heat exhaustion can make you sick, while heatstroke can kill you. Knowing the difference in their symptoms can be lifesaving.

The first signs that you may be overheating are , said Dr. Bjorn Peterson, an with HealthPartners.

The next stage is .

"Heat exhaustion is when you start to feel pretty lousy," Peterson said.

Common symptoms include:

- Nausea
- Dizziness
- A gray or pale appearance
- Cool and clammy skin

But even in this condition, you are still able to sweat - one of the ways the body gets rid of heat.

"The water evaporates off our skin and into the air. When it's humid, you can't do that because the in the air is too high. That's what we're getting into this week." Peterson said.

If not treated, heat exhaustion can turn into the far-more-serious heatstroke. That occurs when a body cannot cool quickly enough and the rises to a dangerous level.

Typical signs of heatstroke are:

- Hot and dry skin
- Confusion
- Rapid pulse

At that point, it's a medical emergency and immediate action is needed.

Get folks showing signs of heatstroke out of the sun and into the shade and call for medical help, Peterson said. Also, cool them off quickly by dousing them with cold water and putting fans on them. Or put them into a bathtub with ice water.

Fitness enthusiasts who insist on exercising outside this week should take some precautions to avoid medical problems, Peterson advised. Drink plenty of water, but don't wait until you're thirsty, he said. Pre-hydrate and pace yourself during your workout. And listen to your body.

"It's about common sense and knowing your body's limits," Peterson said.