A severe heat wave sweeping across the eastern United States is expected to reach its peak over the Fourth of July holiday, breaking temperature records, putting pressure on electricity supplies, and exposing millions of people to dangerous heat conditions.

According to a new study by the scientific group World Weather Attribution, the extreme temperatures and humidity experienced this week would have been almost impossible without the effects of climate change driven by fossil fuel emissions.

The heat wave is being fueled by a powerful heat dome, an area of high pressure that traps hot, humid air over the region. While heat domes are a natural weather phenomenon, researchers say human-induced climate change has made this one significantly more intense.

Climate scientist Friederike Otto said the impact of climate change is no longer a distant threat but is already affecting daily life, from disrupting holiday celebrations to creating unsafe conditions for outdoor sporting events. She stressed that reducing greenhouse gas emissions is essential to prevent even more severe heat waves in the future.

Cities including Washington, D.C., Philadelphia, New York City, and Boston are forecast to experience temperatures close to or above 100°F (38°C), with humidity making it feel even hotter. Heat index values could climb above 105°F (41°C) in several locations.

The soaring temperatures have increased electricity demand as residents rely heavily on air conditioning to stay cool, placing additional strain on power grids across the Northeast and Mid-Atlantic.

Health experts warn that extreme heat remains the deadliest weather-related hazard in the United States. High humidity limits the body's ability to cool itself through sweating, while warmer nights reduce opportunities for recovery. Older adults, young children, outdoor workers, and people without access to air conditioning face the greatest risk.

Authorities are urging people to stay hydrated, reduce outdoor activities during the hottest parts of the day, take regular breaks in cool or shaded areas, and never leave children or pets inside parked vehicles.