A dangerous heatwave is set to engulf much of the central and eastern United States this week as a 'heat dome' settles over the region, bringing scorching temperatures and high humidity ahead of the Fourth of July weekend and FIFA World Cup matches in several US cities.

Forecasters warn that in some places, it could feel as hot as 115 degrees Fahrenheit (46 degrees Celsius). The National Weather Service (NWS) says dozens of temperature records could be broken, with more than 60 million people currently under heat alerts.

A heat dome is a large area of high pressure that acts like a lid, trapping hot air near the ground. As the air sinks, it compresses and warms further, while preventing cooler air and storms from moving in, creating a feedback loop that prolongs heatwaves.

The hottest conditions are expected Thursday and Friday, but the heat will persist through the Fourth of July weekend, which marks the 250th anniversary of the US. Washington, DC, plans the largest fireworks display ever on the National Mall, coinciding with temperatures exceeding 100°F (38°C).

Major cities including New York, Philadelphia, Washington, Chicago, Detroit, and St. Louis are expected to be affected. In Philadelphia, organizers have adjusted Fan Festival hours for World Cup events due to the heat.

'This heat could impact everyone, not just vulnerable groups,' said NWS meteorologist Bryan Putnam. Overnight temperatures will remain in the 70s°F (20s°C), offering little relief. Cities are opening cooling centers and deploying hydration vans.

Experts advise staying hydrated, avoiding strenuous outdoor activity during peak heat, and seeking air conditioning. Symptoms like dizziness or lack of sweating require immediate medical attention.

Source: www.aljazeera.com