Lightning strikes to one side as fireworks light up the sky during the U.S. 250th anniversary celebration at midnight on the 5th (local time) in Washington, D.C. [AP=Yonhap News]

A record-breaking heat wave hitting the United States has resulted in a series of casualties, with at least 25 people reported dead.

Furthermore, as the heat wave began to subside, severe thunderstorms and torrential rain swept through the country, triggering flood warnings and causing power outages that left hundreds of thousands of households without electricity.

According to foreign media reports, including NBC and Bloomberg, on the 5th (local time), at least 25 deaths had been linked to the heat wave as of the previous day.

In particular, 22 fatalities were reported in New Jersey alone.

New Jersey officials stated on the 4th that the victims, mostly between their 30s and 80s, were found dead in homes without air conditioning, on the streets, or inside parked vehicles.

The New Jersey Department of Health issued a warning, stating, "This heat wave is not a typical summer event. It can escalate rapidly to a life-threatening level for people and animals of all ages."

In addition, one heat-related death was reported in each of the states of Illinois, Mississippi, and Louisiana.

The heat wave was caused by a heat dome that formed extensively from the Midwest to the East Coast. On the 3rd, temperatures in New York soared to about 38 degrees Celsius (100 degrees Fahrenheit), with a heat index reaching 43 degrees Celsius (109 degrees Fahrenheit).

Washington, D.C., Philadelphia, and Boston also saw temperatures either break historical records or reach near-record levels.

A street in Manhattan, New York, suddenly hit by heavy rain on the 3rd (local time) [Reuters=Yonhap News]

Due to the heat wave continuing through the Independence Day holiday, several outdoor events were canceled or scaled back.

At the U.S. 250th anniversary celebration at the National Mall in Washington, D.C., so many people suffered from heat-related illnesses that the National Guard was called in for emergency support. NBC reported that chairs at the venue, heated by the midday sun, reached temperatures as high as 70 degrees Celsius (158 degrees Fahrenheit).

On top of this, the region was hit by strong thunderstorms and heavy rain.

A cold front carrying cool air from the north collided with the remaining hot and humid air, creating a powerful storm front that caused further damage.

The U.S. National Weather Service (NWS) issued flood warnings for the New York City area as strong thunderstorms that originated in Ohio moved across the East Coast, including New York, New Jersey, and Connecticut.

Forecasters predicted wind gusts of up to 95 km/h (60 mph) and frequent lightning in some areas, with up to 100 mm of flash flooding expected in parts of Manhattan and Queens.

The high winds and thunderstorms caused power outages primarily in Michigan, New Jersey, and New York, affecting approximately 900,000 households.

Major rail services, including Amtrak and NJ Transit, also experienced significant delays.

Additionally, 511 reports of wind-related damage were filed across the Northeast and mid-Atlantic coast on the 4th, including uprooted trees and downed utility poles.

The NWS advised caution, noting that while daytime temperatures are expected to drop slightly as cooler air from the north moves in, high temperatures and humidity will persist at night, raising concerns for further heat-related issues.