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Q&A: What's this 'feels like' temperature all about?

HOUSTON – When the weather heats up and the humidity climbs, you’ll often hear meteorologists talk about the “feels like” temperature.

That term, which you hear a lot during a Houston summer, is another way of talking about what is formally known as the heat index.

So what does it mean? Here’s what you should know about the heat index and its impact on you.

What is the heat index?

The heat index is a measure of how your body perceives temperature when the humidity, or the amount of moisture in the air, is taken into account. That’s why you’ll hear meteorologists refer to this value as the “feels like” temperature.

Here’s a chart that shows the calculation behind the heat index.

Why is it important?

The higher the heat index, the harder your body must work to keep you cool. The harder your body works, the easier it is for you to suffer from heat-related illnesses.

How does my body keep me cool?

Humans cool down through a process known as evaporative cooling. Basically, when you sweat, those beads of salty water evaporate from the surface of your skin, taking heat away in the process.

When the air surrounding your body is dry, the water is able to easily evaporate. However, when the air is humid, your sweat has a much harder time evaporating, and therefore it's more difficult for your body to cool down.

All of that sweating also strips your body of water, so it’s vitally important to stay hydrated on days when the heat index is high.

What are the symptoms of heat-related illness?

If your body can’t effectively regulate heat, you’ll begin to suffer the symptoms of heat exhaustion.

According to the Mayo Clinic, these symptoms can include:

  • Clammy skin with goosebumps even when you’re in the heat
  • Profuse sweating
  • Faintness
  • Dizziness
  • Fatigue
  • Weak and rapid pulse
  • Low blood pressure when standing
  • Muscle cramps
  • Nausea
  • Headache

If you’re outside and start experiencing any of these symptoms, you should stop what you’re doing, move to a cooler place and drink cool water.

Call your doctor right away if your symptoms don’t improve.

How do I stay safe when the heat index is high?

First and foremost, stay hydrated. That means drinking lots of water and other non-alcoholic, non-caffeinated beverages. 

You should also wear lightweight and light-colored clothing and take frequent breaks in the shade or air-conditioning.

If you begin experiencing symptoms of a heat-related illness, stop what you’re doing, seek shelter in a cooler area and drink cool water. If your symptoms don’t improve, contact a doctor right away.


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