Heat Stress on the Rise: How to Stay Safe From Heat Waves

Heat waves are becoming more common in many parts of the United States. A heat wave is defined by NOAA as ‘a period of unusually hot weather that typically lasts two or more days’. To be considered a heat wave, these high temperatures would have to be outside the historical averages of a given area.

Kitty Gifford

Aug 23, 2022 • Updated May 12, 2023 • 5 min read
Natural Hazards
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Heat waves are becoming more common in many parts of the United States. A heat wave is defined by NOAA (National Oceanic and Atmospheric Administration) as ‘a period of unusually hot weather that typically lasts two or more days.’ To be considered a heat wave, these high temperatures would have to be outside the historical averages of a given area. High temperatures can cause severe illness if the body is not able to sweat and cool down. High humidity increases the risk because sweat cannot evaporate as quickly. According to federal data, approximately 1300 people are killed in the US by extreme heat every year. With heat stress on the rise, staying hydrated and avoiding strenuous activity are key to practicing heat safety.

Summer is getting hotter, sooner#

Across the country, heat waves are arriving more frequently, more intensely and earlier in the year. In other words, the summer season is creeping into spring, extending into fall, and shortening winter. Heat waves occurred on average twice per year in the 1960s; by the 2020s at least six occurred per year, according to the US Environmental Protection Agency. And, EPA data show that nighttime temperatures are rising slightly faster than daytime temperatures in most parts of the country, which makes it harder for people to cool off.

This figure shows changes in the number of heat waves per year (frequency); the average length of heat waves in days (duration); the number of days between the first and last heat wave of the year (season length); and how hot the heat waves were, compared with the local temperature threshold for defining a heat wave (intensity). These data were analyzed from 1961 to 2021 for 50 large metropolitan areas. The graphs show averages across all 50 metropolitan areas by decade.

What causes heat waves?#

Heat waves are caused when domes of high pressure trap hot air. Several factors contribute to the increased frequency and intensity of heat waves. One big factor is climate change, caused in part by the burning of fossil fuels, which has led to an increase in the number of days when the temperature reaches above 30°C (86°F). Since 1900, the world has warmed by more than 1 degree Celsius (about 1.8 degrees Fahrenheit), and the trend has accelerated in recent decades. This warmer baseline helps make periods of extreme heat more frequent and intense.

Another factor is increasing urbanization, as cities tend to be warmer than rural areas because of the concentration of buildings and limited greenery. When trees and vegetation are replaced by roads, buildings, and other structures, natural cooling effects are lost.

Find out how hot it really is – What is the heat index?#

The heat index is a true measure of how the air feels because it combines the air temperature and relative humidity. National Weather Service heat alerts are mainly based on heat index values.

The heat index chart allows you to determine the heat index temperature. Heat and humidity information and forecasts for your area can be found in the local news or on the National Weather Service's website.

In the top row of the heat index chart is the air temperature, on the left side is relative humidity. You find the air temperature and the relative humidity, and you find where they match. For example, if your local temperature is 92°F and the relative humidity is 65 percent, the heat index – how hot it feels to your body – is 108°F. The heat index is also helpful when deciding whether to go out into the sun or stay inside. You should avoid going outside if possible during extreme temperatures combined with high humidity because you run the risk of a heat disorder. A note of caution, the heat index values in the chart are for shady locations. In direct sunlight, the heat index value can increase by up to 15°F.

The following are the perceived temperature ranges at which prolonged exposure or strenuous physical activity can cause problems:

Table showing the four Heat Index classifications and temperature ranges: Caution (80°F - 90°F) Fatigue Possible; Extreme Caution (90°F - 103°F) Heat Stroke, Heat Cramps, or Heat Exhaustion Possible; Danger (103°F - 124°F) Heat Cramps or Heat Exhaustion Likely, Heat Stroke Possible; Extreme Danger (125°F or higher) Heat Stroke Highly Likely

Your Home and Heat Waves#

Health & Safety#

Heat waves are increasing in frequency and severity, so it's important to know how to protect yourself against them. Heat concentrates when no breeze or wind dissipates hot air. In particular, the air inside homes and cars can become very hot and humid, making breathing difficult.   

In hot weather if you exercise or otherwise exert yourself your body is less able to cool itself efficiently. As a result, your body may develop heat cramps, the mildest heat-related illness. Signs and symptoms of heat cramps usually include heavy sweating, muscle cramps, fatigue and thirst. Heat exhaustion signs are characterized by heavy sweating, heat cramps, and a rapid pulse caused by your body overheating. Heat strokes are the most severe heat-related illnesses and can cause death or permanent disability if untreated. Symptoms of heat stroke include high body temperature (103°F or higher), fast pulse, headache, dizziness, nausea, or confusion.

There are a number of heat stress safety tips suggested by experts that you can do to stay safe from heat waves and extreme heat.  

  • Stay hydrated and drink plenty of water

  • Try to avoid strenuous activity outdoors during the hottest part of the day

  • Close doors and windows if air outside is hotter than inside

  • Use fans or air conditioners (when the temperature is above 95°F, fans aren’t effective) 

  • If you can’t cool your home and an air conditioner is not available, check your area for designated cooling centers or visit a public library or shopping mall

  • Turn off lights and appliances that aren't being used

  • Wear light clothing and sunscreen when outside

  • Know the warning signs of heat exhaustion and heatstroke

The effects of heat waves are more than just uncomfortable. They can cause illness and even death, particularly among the very young (infants and children up to four years of age), people 65 years of age and older, and other vulnerable groups. According to the Centers for Disease Control (CDC), elderly people are more likely to suffer from heat-related health problems during extreme weather events like heat waves.  If you live near an elderly person, especially one that cannot move around easily, you might check on them during heat waves. 

Property Values#

Due to the unpredictability of climate change, it is difficult to evaluate the risk for specific events to occur at any particular property. A recent study projected that the number of days with heat indices exceeding 100°F and 105°F would double and triple, respectively, by mid-21st century (2036–2065) compared to a 1971-2000 baseline. Many real estate professionals expect that in coming years, people will migrate to areas of the country that are less impacted by heat, or other climate-related events but the extent to which population shifts will occur is difficult to predict. AreaHub reports can help consumers make more informed choices by reviewing potential extreme weather hazards in a given location. Homebuyers can factor in additional costs to adapt homes for climate change hazards such as heat waves, as well as higher electricity expenses to cool buildings. 

A study predicts that the global air conditioner market will grow more than 5% by 2026. While homebuyers are generally concerned about a home’s air conditioning system, they don’t expect to replace it right away, however if it’s a newer system with smart technology or energy-efficient, buyers consider that a perk. For sellers, energy-efficient amenities such as air conditioners, insulation, and double-paned windows are worth highlighting. According to Energy Star, “EPA estimates that homeowners can save an average of 15% on heating and cooling costs (or an average of 11% on total energy costs) by air sealing their homes and adding insulation in attics, floors over crawl spaces, and accessible basement rim joists.”

Overall, buyers and renters prefer buildings and developments designed for comfortable indoor temperatures. Extreme heat-related risks from increased wildfire and drought risks can also impact consumer preferences.  

What You Can Do#

Heat stress can affect anyone, but older adults, young children, and people with chronic illnesses need to take extra precautions. This includes drinking enough fluids, avoiding strenuous activities, wearing lightweight clothing, and using air conditioning. Also, check with your doctor before taking any medications that might affect your ability to regulate body temperature. While some people are at greater risk, no one is immune from heat-related problems. When people overheat, they may get dizzy or confused and be unable to recognize they are unsafe.

Remember that a person who lives in a warmer climate is accustomed to higher temperatures than one who lives in a colder climate. As a result, what is considered normal in one area may be unusually hot in another.

Seek Medical Attention#

If you feel ill while outside, seek immediate medical help. While heat-related illnesses are preventable, it is important to learn the warning signs and symptoms of heat stress that can result in heat stroke, heat exhaustion, heat cramps, and sunburn.

Prepare Your Home#

If you live in an area where temperatures regularly reach 90 degrees Fahrenheit or higher, insulating floors and ceilings will help keep you cool in the summer and warm in the winter. This is especially helpful when you’re using fans or air conditioners to cool down your home.

There are small window and portable A/C units that are more energy-efficient than whole home central air conditioning systems. Visit the Energy Star program for products that meet strict energy-efficient specifications the U.S. EPA sets. 

You can also work with a heating and cooling contractor to help choose equipment that is properly sized for your home and follows Energy Star guidelines.

According to the U.S. Department of Energy, about 76% of sunlight that falls on standard double-pane windows enters to become heat. Keep windows and doors closed as much as possible to prevent outside air from entering your home. Adding window coverings with light-colored linings can help to reduce the solar heat gain. Window coverings include curtains, blinds, shades, or tinted window film.

Rather than heating up your home with stovetop and oven cooking, opt for using a microwave, induction cooktop, toaster oven, or electric pressure cooker.

Get Assistance with Utility Bills#

Don't let energy costs keep you from using life-saving tools. Contact your utility company about flexible billing and payment programs. They can also direct you to available assistance programs.

AreaHub’s Knowledge Center is updated regularly and provides information drawing upon scientific studies and sources.

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