What’s worse is the threat of serious harm from getting too hot during this hot season. 
What is heat stroke? 

— Heat stroke serious strikes when a person's body gets too hot. Most often, heat stroke happens when people exercise in very hot, humid weather without drinking enough fluids. But heat stroke can also hit people who are simply in the heat and cannot sweat or cool off enough. It is especially likely to affect older people and people who have health problems, who need to be extra careful in hot conditions.

Heat stroke is a medical emergency that needs to be treated quickly because this overheating can lead to death if it is not treated quickly.
When people get too hot, they can also get "heat cramps" and "heat exhaustion." These conditions are not as serious as heat stroke, but can lead to heat stroke if they aren't handled quickly.

What are the symptoms of heat stroke? — People with heat stroke have:
●A body temperature of 104°F (40°C) or higher
●Brain symptoms – These can include:
 •Confusion or trouble thinking clearly
 •Hallucinations (seeing or hearing things that aren't real)
 •Trouble walking
 •Seizures
 •Passing out
Heat stroke can also cause:
●Fast breathing or a fast heartbeat
●Skin redness and warmth
●Vomiting or diarrhea
●Muscle cramps or weakness
●Headaches
Should I see a doctor or nurse? 

— Yes. If you or someone you are with has heat stroke, get medical help right away. You should call 1-1-5 for an ambulance right away.
Is there a test for heat stroke?

 — Yes. The doctor will do an exam and take your temperature. He or she will probably do other tests to check if the heat stroke has damaged other organs in your body. These tests can include:
●Blood tests
●Urine tests
●Chest X-ray
●Electrocardiogram (ECG or EKG) – This test measures the electrical activity in your heart (figure 1).
Person having an ECG
 
How is heat stroke treated? 

— The main treatment involves cooling your body down. Your doctor can do this in the hospital in different ways.
Your doctor will also treat any other problems the heat stroke has caused.
Can heat stroke be prevented? 

— Yes. When it is hot or humid outside, you can do the following to prevent heat stroke:
●Limit strenuous activity, and take breaks when you exercise.
●Drink enough fluids, such as water or sports drinks, so you do not feel thirsty. But don't force yourself to drink very large amounts in a short time, and don't drink so much that you feel uncomfortable.  A useful guide to the right amount of fluids is when your urine is a light yellow.
●Do your heavy exercise early in the day, before it gets too hot out.
●Wear loose, lightweight clothes. Don't wear too many layers.
●Avoid being in a hot car that cannot cool down.
 • Definitely do not leave your kids or pets in a hot parked car.
●What you should know about heat cramps and heat exhaustion: Heat cramps are painful muscle cramps. Heat exhaustion can cause headaches, dizziness, nausea, or vomiting. It can also make you thirsty or tired.
●If you have symptoms of heat cramps or heat exhaustion, you should cool your body down right away to avoid getting heat stroke.
To cool your body down, you can:
●Spray yourself with cool water and then sit in front of a fan.
●Move into the shade, or go into an air-conditioned building or car.
●Take a cool shower or bath.
●Drink water or a sports drink. Do not have a drink with alcohol or caffeine.
●Take off any extra clothing you are wearing.
●Put a cold pack or cool cloth on your neck or armpits.

Source: UpToDate