The Facts About Heatstroke and the Heat Index

Heatstroke is dangerous and it can come on fast without you knowing it. Understanding what the heat index means can also prepare you and help you avoid heatstroke.

Heatstroke is dangerous and it can come on fast without you knowing it. Understanding what the heat index means can also prepare you and help you avoid heatstroke.

The Heat Index

During the winter we have the wind chill factor which tells us how the wind combined with the temperature can affect our skin and our health. During the summer we have what is known as the heat index.

The heat index is the combination of the air temperature and the humidity and how it affects our skin, body and health. The National Weather Service (NWS) will give you the heat index along with other readings every hour. The higher the humidity the higher the heat index will usually be. For example, if it is just 90 degrees F with a humidity of 60%, it will actually feel like it is 100°F. Raise the humidity to 70% and the heat index jumps to 109°F. So an air temperature of just 90°F can actually affect your body as if it was 109°F.

The heat index was devised for the shade and light winds, being in full sunshine can increase this heat index temperature by as much as 15°F.

This is why it is important to understand and pay attention to the heat index. A heat index at or above 105°F is in the danger category and can cause heatstroke. The NWS will issue excessive heat watches and heat warnings when dangerous heat is expected or occurring.

Heat and Heatstroke Kills People

Hot weather especially combined with higher humidity should not be taken lightly. In the United States, heatstroke is the number one weather related cause of death. In the US, a 10-year average shows that heat and heatstroke killed on average 237 Americans per year. In the 1980 heat wave, 1,270 Americans were killed and in the 1995 heat wave, more than 700 people died in Chicago alone. The United States isn't the only place where heatstroke is a concern. In 2003, a severe heat wave hit Europe where an estimated 50,000 people were killed by heatstroke and heat related health problems.

The Cause of Heatstroke

Heatstroke occurs when the body's ability to cool itself starts to fail. Our body keeps cool during excessive heat by sweating and circulatory changes. The circulatory changes are when the capillaries begin to dilate or open up to dissipate heat. This causes the sweat glands to draw water from the blood so it can put water on our skin to cool us. Our body will pump more blood to keep the body cool, this is why excessive heat can put a strain on the heart. A healthy heart is more able to keep up with the demand of the body's need to pump blood during heat. The older you are, the more susceptible to heat illness and heatstroke you are.

When the sweat on your body evaporates it turns into water vapor and this process takes energy which cools your skin and body, the energy of evaporation takes heat off of your body. When the humidity is high and the heat index is high, this evaporation might not occur or occur as quickly. Even though the sweat isn't evaporating at a normal rate under high humidity and temperature, your body continues to sweat. And the hotter your body is getting the more you are sweating.

When we sweat, we are losing water and minerals and the loss of these minerals causes an imbalance in our body which can lead to heat related illness including heatstroke.

NWS local observations for New Orleans. HX is the heat index.

Stages and Symptoms of Heatstroke

Heatstroke can begin with muscle cramps, headaches and fatigue brought on by the start of dehydration.

Stage two is heat exhaustion and is characterized with more water and mineral loss (electrolytes) through excessive sweating. The symptoms of heat exhaustion are excessive sweating, dizziness, disorientation, lethargy and vomiting. The skin sometimes can actually feel cool.

Stage three is heatstroke and the symptoms are the above symptoms and possibly a body temperature of 105°F, rapid shallow breathing, seizures and possibly coma. In children, the symptoms can include an inability to sweat any more.

How to Prevent Heatstroke

Excessive heat and sweating actually causes the volume of blood to drop along with minerals and the all important water. If this continues, dehydration starts with muscle cramps. These minerals include salt or sodium, potassium, magnesium and calcium. When dehydration continues it progresses into the various stages of heat illness and heatstroke.

This is why you have to drink plenty of water, even if you're not thirsty. We hear this so much that we ignore it anymore. We need to drink a lot of water on these hot days and nights especially when the heat index is high with high humidity. By drinking plenty of water we are replenishing exactly what our body needs to keep us cool. Use the following tips to prevent heatstroke.

  • Drink plenty of water
  • Avoid alcohol, alcohol is dehydrating and will make the heat worse.
  • Eat smaller and lighter meals. Eating a heavy meal or a meal high in animal protein will cause your body to become hotter while digesting the food.
  • Take breaks, find shade and rest until you cool down.
  • Dress lightly and in light colored clothes, wearing a hat can help keep the hot sun off of your head.
  • Go to an air conditioned mall, ice rink or friends house with air conditioning during a heat wave.

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