What is the heat index? (2024)

FAQs

What is the index for heat? ›

The heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature. This has important considerations for the human body's comfort. When the body gets too hot, it begins to perspire or sweat to cool itself off.

Understand heat index danagers: Avoid running outside if the heat is above 98.6 degrees and the humidity is above 70-80%. If the humidity in the air is so high that it prevents the process of evaporation of sweat from the skin, you can quickly overheat and literally cook your insides from an elevated body temperature.

less than or equal to 55: dry and comfortable. between 55 and 65: becoming "sticky" with muggy evenings. greater than or equal to 65: lots of moisture in the air, becoming oppressive.

This is called the heat index and is due to the increased moisture in the air limiting the body's ability to cool off through sweating. When the heat index reaches 105° F, or higher, conditions can become dangerous for both people and pets.

The current official highest registered air temperature on Earth is 56.7 °C (134.1 °F), recorded on 10 July 1913 at Furnace Creek Ranch, in Death Valley in the United States.

Using this table, we can quickly see that, on a hypothetical day with an air temperature of 90 degrees F and humidity of 80 percent (not a completely unreasonable scenario in Houston), it would feel like it is 113 degrees F outside.

Your thermostat may say 75°, but you could still feel overheated if you have moist air inside. With air conditioning and humidity, how hot you feel, known as the heat index, is what matters when it comes to comfort. The better question is: Does the heat index affect air conditioning? Yes, it does.

High humidity, over 45 percent, can leave rooms feeling clammy and sticky which can be unbearable. A humidity level of over 50 percent isn't just uncomfortable, it can also cause health issues and higher HVAC system bills.

A new study suggests that once temperatures hit 104 to 122 degrees, our bodies may stop working optimally.

How hot does it have to be before it's safer to be inside? Oller points to the heat index for this one: Temps between 90 and 105 degrees Fahrenheit are considered “extreme caution,” and anything above falls under the “danger” and “extreme danger” categories.

What should I set my thermostat to in extreme heat? ›

The best temperature settings when you're at home

To stay comfortable and save money, the U.S. Department of Energy recommends the best AC setting during summer is 78°F (26°C) when you are home. Setting your air conditioner to this level will allow you to stay cool and avoid an unusually high electricity bill.

Everyone is different, and that's definitely true when it comes to ideal room temperature. That being said, the average room temperature in most homes falls somewhere between 68 and 76°F. (Interested in learning more about home automation and how it could benefit your family?

Energy.gov suggests that 68 degrees is a good room temperature while you're awake at home but recommends lowering it while you're asleep or away. Lowering your thermostat 7-10 degrees for eight hours a day can reduce your annual heating expenses by as much as 10 percent.

Then your brain just goes right off to lunch and you have a hard time thinking at all. The WMO, which keeps official global weather records, places the hottest temperature ever measured on Earth at 134 degrees F; this reading was taken in Death Valley on July 10, 1913.

Heat Index: 130+ degrees F Health Effect: Heatstroke/sunstroke is highly likely with continued exposure Recommendations: Avoid strenuous outdoor activity. Stay indoors in an air conditioned facility. Stay well-hydrated. Drink 10 gulps every 20 minutes.

A temperature of 96°F (35.5°C) is considered low. It's important to recheck the temperature to make sure it is not a false reading. That said, 96°F (35.5°C) is not substantially low, so if you're not having any other concerning symptoms, it is, most likely, not something to worry about.

For example, an air temperature of 90° F and a relative humidity of 60% intersect at a heat index of 100°. In other words, the temperature would feel like 100° with this humidity/temperature combination. Heat index values were devised for shady light wind conditions.

In the National Risk Index, a Heat Wave Risk Index score and rating represent a community's relative risk for Heat Waves when compared to the rest of the United States.