What is a hot dome? The US heatwave described | Weather News

Strong temperature is expected to cover much of the central and eastern United States this week as a “tropical center” settles into the region, bringing very hot and humid days ahead of the Fourth of July weekend. FIFA World Cup matches in several US cities.

Forecasters say temperatures will reach as high as 46 degrees Celsius (115 degrees Fahrenheit) in some places. More heat records could be broken, according to the National Weather Service (NWS), which called it “dangerous”. More than 60 million people are currently on heat alerts.

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At the center of this week’s forecast is a weather phenomenon known as a heat dome. What is it, and why does it make heat waves so intense and unbearable?

What is a hot dome?

A heat dome is a large area of ​​high pressure, which is formed when warm air flows northward, which acts as a lid on top of the atmosphere, trapping hot air near the ground.

As the air sinks, it compresses and heats up. At the same time, the pressure system helps to keep cold air and storms from moving, which causes the heat to stick to the surface and stay there. With less cloud cover and less wind, the sun has more access to the ground, creating a sense of warmth.

Dome heat is associated with long periods of heat that last for days.

How long will it take?

A heat dome is already building and is expected to strengthen in the coming days, spreading from the central US to the east coast, with extreme heat lasting several days until early July.

Warmer conditions are expected Thursday and Friday, according to the NWS, and should continue through Sunday, the Fourth of July, which is the 250th anniversary of the U.S., and forecasters say areas across the Great Plains, Southeast, and mid-Atlantic are expected to remain unseasonably warm through the end of next week.

What will the maximum temperature be?

Most areas are expected to see daytime temperatures in the upper 30s Celsius (low 100s Fahrenheit), but humidity will make it even hotter. In some parts of the central and eastern US, the temperature index – a measure of how hot it feels when humidity sets in – can rise between 40C and 46C (100F and 115F).

“This heat wave affects everyone,” said NWS meteorologist Bryan Putnam. “It’s not just old people or young children or people who spend a lot of time outside, maybe they are strengthening themselves more than they usually do.

The nights will also bring no relief, with temperatures expected to stay in the 20s Celsius (70s Fahrenheit) overnight, making for miserable sleep for those without air conditioning and making people suffer from the cold.

“Even after the sun goes down, it’s still very hot,” said AccuWeather meteorologist Alan Reppert. “We’re on track for the hottest part of the day and into the evening.”

Which parts of the US will be most affected?

The worst conditions are expected in a wide stretch from the Great Lakes to the East Coast, where several cities could experience their hottest day of the year so far. New York City, Philadelphia, Washington, Baltimore, Chicago, Indianapolis, Detroit and St Louis are all expected to be affected, and temperatures will rise further south in Dallas, Little Rock and Memphis.

Many of these cities are also hosting FIFA World Cup events. In Philadelphia, the editors have already changed Fan Festival hours begin at noon.

Cities across the US are developing emergency measures as temperatures rise.

Chicago said it would open a cold storage facility and send city workers to check on vulnerable people.

In New York City, Mayor Zohran Mamdani’s office announced what it called an “unprecedented” response to the heat, including hydration vans and cooling stations equipped with crazy fans and cool towels.

In Washington, DC, where temperatures are expected to exceed 38C (100F) from Thursday to Saturday, the heat will coincide with Fourth of July celebrations, including what organizers say will be the largest firework display ever held on the National Mall.

What are some ways to stay cool?

The NWS says people should stay hydrated, avoid outdoor activities during extremely hot weather and seek air-conditioned or cooler areas if possible. If you are staying outside, wear loose, light clothing and stay near the shade.

Experts say that one of the biggest risks of prolonged heat is that the body does not have time to cool down overnight, which can cause the effects of heat to rise from one day to the next. They also recommend drinking water before you feel thirsty and cutting back on alcohol, which can increase the risk of dehydration.

“If someone notices that they’re hot, but they’re not sweating, or if they start to feel a little dizzy, those are signs that they really need to take a break, get inside, get cool, and drink more water,” said Geoff Cornish, senior assistant video meteorologist for weather forecasting company AccuWeather. “And if they start to have serious symptoms, they should go to the hospital immediately.”