What is a heat dome? Scorching temperatures forecast for Greenville, Upstate SC (2024)

A heat wave is a period of unusually high temperatures over a region. As temperatures cook on the Midwest and Northeastern coast, the term "heat dome" has been used to describe the hot weather, leaving many questions to be answered.

The National Weather Service (NWS) has issued a hazardous weather outlook from Friday, June 21 through Wednesday, June 26 for Northeast Georgia, the North Carolina foothills and Piedmont, and Upstate South Carolina.

High temperatures are forecast to reach the mid 90s Saturday through Monday, with heat indices expected to reach 100 to 104 degrees. Those who are sensitive to the heat will want to decrease their time spent outdoors to prevent heat-related illnesses.

Here's what to know about the heat dome and how you and your family can stay safe in it.

What is a heat dome?

Per AccuWeather, the term "heat dome" is used to describe a sprawling area of high pressure promoting hot and dry conditions for days or weeks at a time. It is similar to a balloon in the way it expands and contracts as the day goes on. When a certain area is inside it, it can feel very warm. A heat dome can interfere with the production of clouds, leading to an increase in sunlight and high temperatures. In turn, the cooling demand will increase, which may boost the strain on a region's power grid. Drought conditions may also develop due to extended dry and hot spells.

More: It's getting hot out: Here are the best settings for your air conditioner in South Carolina

What are 'ring of fire' thunderstorms?

Since heat domes act as large, immovable bubbles, moisture is forced up and over the heat bubble, according to AccuWeather. This causes "ring of fire" thunderstorms to form along the fringes of heat, which may bring severe weather into the area.

"Let's say, for example, you had a big high pressure over the Southern Plains, Texas, or Oklahoma. What will happen is, on the northern fringes of higher pressure, you'll get these periods of thunderstorms that develop, maybe over the Central Plains. It will move around the periphery of that high pressure, which tends to be in kind of a circular shape, hence the ring terminology to it." said Thomas Winesett with the NWS at Greenville-Spartanburg International Airport.

Ring of fire features are currently favorable for the Midwest and parts of the Ohio Valley due to centered high pressure activity in both areas. As the heat dome ensues, will South Carolina also get a chance for severe weather?

"That's not to say we can't get some thunderstorms, but it won't be the true ring of fire type storms maybe until later, later next week if that high pressure shifts back off to the west or Texas, New Mexico." Winesett said. "So when that happens, that might allow us to get into a more active pattern where we see those ring of fire type storms maybe coming more out of the Mississippi Valley and Tennessee Valley and towards the Appalachia."

More: 5 best waterfalls in the Upstate: See the tallest, falls with short hikes, more

When will the heat dome end?

Doug Outlaw with the NWS at GSP said he hopes current weather conditions do not stick around for too much longer, especially with the reestablishment of high temperatures next weekend. Next Friday's heat will bump down a few degrees before temperatures continue to soar. The timing of a cool down period remains uncertain.

"It is typical to have heat waves on and off during the summer, but we hope that the weather doesn't get stuck and we end up way up in the 90s every day for weeks," he said. "But we've got to be prepared for the possibility of something like that."

Outlaw forecast the following high temperatures for Greenville heading into next week:

∎ Friday, June 21: 91 degrees

∎ Saturday, June 22: 93 degrees

∎ Sunday, June 23: 94 degrees

∎ Monday, June 24: 95 degrees

∎ Tuesday, June 25: 95 degrees

∎ Wednesday, June 26: 96 degrees

∎ Thursday, June 27: 95 degrees

Types of heat warnings issued by the National Weather Service

The NWS issues several types of heat advisories depending on severity. The different types are as follows:

∎ Excessive heat warning: This warning is issued 12 hours of the onset of extremely dangerous heat conditions. When the maximum heat index temperature is expected to reach 105 or higher for at least two days and the nighttime temperature will not drop below 75, the warning is issued. This rule may vary across the country, especially for areas not used to extreme heat conditions. Precautions should be taken immediately during extreme conditions to prevent serious illness and even death.

∎ Excessive heat watch: A watch is issued when an excessive heat event is favorable within the next 24 to 72 hours. When the risk of a heat wave has increased but the occurrence and timing is uncertain, a watch is issued.

∎ Heat advisory: An advisory is issued within 12 hours of the onset of extremely dangerous heat conditions. When the maximum heat index temperature is anticipated to be 100 degrees or higher for at least two days and the nighttime temperature will not drop below 75 degrees, an advisory is issued. This rule may vary across the country, especially for areas not used to extreme heat conditions. Precautions should be taken immediately during extreme conditions to prevent serious illness and even death.

∎ Excessive heat outlook: An outlook is issued when there is a potential risk for an excessive heat event within the next 3-7 days, providing information for those who need considerable lead-time to prepare for the event.

High temperatures forecast across US Midwest, Northeast

These are the high temperatures forecast for several Midwest and Northeast cities from Juneteenth and June 20. Temperatures will dip between this week and early next week, according to a USA TODAY story:

∎ Manchester, New Hampshire: 97, 99. Dropping to 86 by June 24.

∎ Albany, New York: 96, 97. Dropping to 86 by June 24.

∎ Detroit, Michigan: 95, 93. Dropping to 83 by June 24.

∎ Toledo, Ohio: 94, 96. Dropping to 84 by June 24.

∎ Indianapolis, Indiana: 92, 95. Jumping to 96 by Saturday, June 22 before dropping to 97 on June 24.

∎ Caribou, Maine: 96, 95. Dropping to 76 by June 24.

∎ Philadelphia, Pennsylvania: 94, 95. Jumping to 100 by Friday, June 21 before dropping to 90 on June 24.

∎ Boston, Massachusetts: 95, 97. Dropping to 85 by June 24.

∎ Washington, D.C.: 90, 92. Jumping to 98 by Saturday June 22 before dropping slightly to 93 on June 24.

How to prepare for the heat

Tips from NOAA:

∎ Make sure the air conditioner is functioning properly. If your home does not have air conditioning or loses power, visit a designated cooling shelter or other air-conditioned location such as the mall or public library.

∎ Check on friends, families, neighbors, and pets to ensure they are safe in the heat. It is important to check on those who live alone or do not have air conditioning.

∎ Never leave children, dependents, or pets unattended in vehicles. The sun can heat the inside of the car to deadly temperatures in minutes.

∎ Wear loose clothing that is light-colored and covers the skin.

∎ Hydrate with water throughout the day, avoiding caffeine and sugary beverages.

∎ Set aside one gallon of drinking water per person a day in case of a power outage.

∎ Keep out of the sun and stay indoors on the lowest level. Curtains and shades should be closed.

∎ Immerse yourself in a cool bath or shower. Cooling your feet off in water can also help.

∎ If temperatures are cool at night, let the cool air in by opening windows.

∎ If you are outside, stay in the shade. Apply sunblock and wear a wide-brimmed hat before going outside.

∎ To avoid heat exhaustion, do not engage in strenuous activities. Use a buddy system and take breaks in the shade when working in extreme heat.

∎ For critical updates from the National Weather Service (NWS), tune into NOAA Weather Radio.

For more heat safety information, visitweather.gov/heatorheat.gov.

Nina Tran covers trending topics for The Greenville News. Reach her via email at ntran@gannett.com