Heat dome vs. heat wave: What's the difference (and why it matters)?

Over 90 million Americans will be trapped in extreme temperatures this week due to a heat dome forming from Nebraska to Florida, as per a health alert issued by the National Weather Service.

Much of the Mississippi Valley and parts of the Southeast will be facing dangerous heat from Tuesday to Thursday, with temperatures crossing 100 degrees Fahrenheit in some areas. Some places could see heat index values of 110 to 115 degrees.

Areas facing July heat alerts


The corn sweat phenomenon is expected to occur with extreme heat hitting parts of the Corn Belt, a region over part of the Plains and Central Mississippi Valley where high humidity can be expected with a heat index between 105 and 110 degrees. The phenomenon occurs when extreme heat beats down on corn crops, causing them to perspire and increase the humidity in the air.

Recorded high minimums are expected to break in states like Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Missouri, South Carolina and Tennessee, as per Climate Central, a non-profit that analyses climate change data.

According to the NWS Prediction Center, the combination of high humidity and temperatures could lead to an increase in the amount of heat-related health issues.

Climate change is the cause of increased heat waves
Climate change has made excessive heat in July three times more likely for nearly 160 million people in the US, a Climate Central analysis revealed.

For areas from Salt Lake City and Santa Fe, New Mexico, to Tallahassee, Florida and Montgomery, Alabama, human-made climate change has made the extreme heat five times more likely.

In June, another heat dome exposed half of the United States to dangerously high temperatures, with seven states breaking the monthly high temperature records and many even exceeding triple digits.

What is the difference between heat domes and heat waves?

A heat wave is simply a long period of extremely high temperatures in a region. It is defined by the duration, can occur at any time and is just a weather occurrence.

Heat dome, on the other hand, is a meteorological situation where a strong high-pressure system stalls over a region, trapping and compressing the heat like inside a dome. Here, a high-pressure ridge is formed, warm air sinks and can persist for days and weeks. A heat dome is more harmful for health than waves, as these generally have higher heat indexes, stay for longer and are more intense in effect.

While a heat wave can be an effect of a heat dome, the alternative is not possible. Due to its higher intensity, people are more concerned and wary of a heat dome than a heat wave and need to take more precautions to remain safe.

How to stay protected during a heat dome?
According to the Environmental Protection Agency, more than 1,300 deaths per year in the United States are due to extreme heat. Thus, there are some steps one must follow to avoid damaging their health in the excessive heat.

Avoid strenuous outdoor activities during the hottest parts of the day. However, if you must remain outside, take breaks to go cool off in the shade and ensure proper hydration.

Watch out for heat-related illnesses by being cautious of symptoms such as exhaustion, dizziness, nausea, headache and confusion. If you are experiencing any of these symptoms, consult a medical professional immediately.

The importance of hydration during a heat wave can not be underlined and highlighted enough. Even if you don't feel thirsty, ensure that you are constantly drinking plenty of fluids and carry electrolyte drinks of ORS sachets with you when going outside.

Be aware of cool environments in your area. Spend time in air-conditioned places like malls, libraries and cooling centres. Places like Phoenix and even some Northern cities open cooling centres during summers.