A dangerous heat wave is tightening its grip on the East Coast, with the worst conditions arriving as millions prepare to celebrate the Fourth of July outdoors. The heat is expected to peak during one of the busiest travel and outdoor celebration periods of the year, prompting cities to expand cooling centers, shorten parade routes, and activate emergency response plans.

Affected Areas

More than 160 million people are under a Level 3 of 4 ‘major’ or Level 4 of 4 ‘extreme’ heat risk through the end of the week, according to the National Weather Service. Cities such as Boston, New York, Philadelphia, Washington, DC, and Raleigh, North Carolina, are opening cooling centers and expanding public resources as the dangerous heat settles in.

The federal government is also preparing for the strain. The Department of Energy has issued emergency orders aimed at reducing the risk of power outages by increasing electricity generation within the PJM Interconnection grid, which serves much of the Mid-Atlantic.

Heat-Related Illnesses

The heat waves have been triggered by intense heat domes — stubborn areas of high pressure that lock hot air in place — and are clearly supercharged by global warming, experts say. The biggest concern isn’t just the daytime heat. Warm, humid nights will provide little relief, with temperatures only falling into the 70s in many locations and struggling to drop below 80 degrees in urban areas.

Without cooler nights, the body has little opportunity to recover before another day of dangerous heat. It’s the temperatures and the humidity that increase the health risks. High humidity keeps temperatures elevated and prevents sweat from evaporating efficiently, making it harder for the body to cool itself.

Original reporting: KTVZ (Central Oregon) — read the source article.