1)  It can alter your mental state
Heatstroke can cause confusion, agitation, slurred speech, irritability, delirium and seizures, according to the Mayo Clinic in Minnesota. It can even put someone in a coma. If you think someone is suffering from heatstroke, call 911 and try to cool them down, for example by getting them to shade or indoors or cooling them off with water.

2) It can cause nausea, vomiting 
Heatstroke can cause nausea and vomiting. If not treated, it can cause severe injury to internal organs and can even be deadly.

3) Breathing, heart beat speed up
Heat puts tremendous stress on the heart, which works to cool the body, causing a rapid heart beat. It also can cause alter breathing, making it rapid and shallow.

4) The skin turns red, hot or moist
Signs of heatstroke can include flushed skin as the body temperature rises. It can also make the skin hot and dry, or cause profuse sweating during exercise.

5) It can spark headaches
Heatstroke can prompt headaches. If you're exposed to high heat and your head starts to throb, it may be a sign of danger. Get into the shade or go indoors, especially in areas that are air conditioned. Do not wear extra clothing in the heat either.

6) Drink water, not alcohol
On a hot day, it's best to drink water -- not alcohol. Wine and beer, for example, can affect the body's ability to regulate its temperature. Water will hydrate you and help replenish fluids lost through sweat.  

7) Certain medications can contribute to heatstroke
Certain medications can contribute to heatstroke by affecting the body's ability to stay hydrated and respond to heat. People should take care in heat if they take medications that narrow the blood vessels (vasoconstrictors), regulate blood pressure by blocking adrenaline (beta blockers), rid the body of sodium and water (diuretics) or control psychiatric symptoms (antidepressants or antipsychotics). Stimulants for attention-deficit/huyperactivity disorder - ADHD -- and illegal stimulants such as amphetamines and cocaine can also contribute to heatstroke.

8) Age can make you susceptible to heatstroke
The body's ability to cope with extreme heat depends on the strength of the central nervous system. In young children, it's not fully developed, and when people hit 65, it starts to deteriorate. Both groups also usually have a tendency to become dehydrated, thus increasing the possibility of getting heatstroke.  

9) Get cooled down
In extreme heat, stay as cool as possible by avoiding being outside in the fiery sun. Wear a hat and stay in the shade or in water. Staying in an air conditioned space is the best option, but if that's not possible, get near a fan. Doctors might also recommend immersing yourself in cool water or lower the body's temperature with evaporation cooling techniques. This consists of misting water on the skin while being fanned with warm air. Another way to cool down is to apply ice packs to the groin, neck, back and armpits.

10) Seek medical help if you suspect you or someone else has heat stroke
Seriously. (And please don't leave your pet or child in a hot car for any length of time.)