Extreme heat is a period of high heat and humidity with temperatures above 90 degrees for at least two to three days, according to Ready.gov.
While dealing with the extreme heat, knowing the difference between the temperature and heat index can help prepare for the day ahead.
Temperature vs. Heat Index
Air temperature is the actual physical temperature of the air, measured by a thermometer placed under standardized conditions, according to the National Weather Service.
The heat index combines air temperature and relative humidity to estimate how hot conditions feel to people, according to the National Weather Service. High humidity makes it harder for sweat to evaporate, reducing the body's ability to cool
itself. As a result, a day with a temperature of 95 degrees can feel substantially hotter when humidity is high.
Common misconceptions about heat index and temperature:
- The heat index is the real temperature.
- Humidity always makes the heat index higher.
- Heat index works everywhere outdoors.
- Heat index fully captures heat danger.
- If I'm healthy, heat index warnings don't apply to me.
- It's the humidity, not the heat.
Temperature tells you how hot the air is. Heat index tells you how hot that air-humidity combination is likely to feel to a typical person in the shade with light wind, according to the National Weather Service. The biggest public misunderstanding is treating the heat index as an actual temperature measurement rather than a physiological estimate of heat stress.
Since the amount of atmospheric moisture needed to saturate the air depends on the temperature, relative humidity is a function of both moisture content and temperature, according to the National Oceanic and Atmospheric Administration. The warmer the temperature, the more moisture the air can contain before it becomes saturated. Therefore, with the same moisture content, warmer air will have a lower relative humidity than colder air.
Tips to keep cool
- Drink plenty of water throughout the day, even if you don't feel thirsty.
- Limit strenuous outdoor activities during the hottest part of the day, typically between noon and 6 p.m.
- Wear lightweight, loose-fitting, and light-colored clothing.
- Spend time in air-conditioned buildings, such as libraries, shopping centers or community cooling centers.
- Take frequent breaks in the shade if working or exercising outdoors.
- Never leave children or pets in a parked vehicle, even for a short time.
- Check on older adults, young children, and people with chronic health conditions, who are at greater risk for heat-related illnesses.
Extreme summer heat is increasing in the United States, according to the Centers for Disease Control and Prevention. Climate projections indicate that extreme heat events will be more frequent and intense in coming decades.
While better forecasting, early heat warning systems, and increased access to air conditioning have helped to prevent some heat-related illness and death in recent decades, extreme heat events remain a cause of preventable death nationwide.
This reporting content is supported by a partnership with Journalism Funding Partners.
Erica Van Buren is the climate change reporter for The Augusta Chronicle, part of the USA TODAY Network. Connect with her at EVanBuren@usatodayco.com or on X: @EricaVanBuren32.
This article originally appeared on Augusta Chronicle: Hot and humid in Augusta: Why heat index warnings matter
