An intense heat wave is spreading over much of the United States and keeping around 238 million people, equivalent to 70% of the country's population, under weather alerts, while authorities warn that extreme temperatures could break historical records during the Independence Day weekend.

According to the National Weather Service (NWS), a high pressure system known as a heat dome has favored the accumulation of warm air over the center and east of the country, raising temperatures above usual levels and causing heat indices of between 38 and 46 degrees Celsius in many regions.

States with the highest alert level include New York, New Jersey, Massachusetts, Pennsylvania, Ohio, Indiana, Michigan, Georgia, Tennessee, North Carolina, Kentucky, West Virginia, Virginia, Maryland, Alabama and Mississippi, where the combination of heat and humidity poses an elevated health risk, especially among older adults, children, people with chronic illnesses and outdoor workers.

In New York City, temperatures near 100 degrees Fahrenheit were forecast, with a wind chill of up to 111 degrees, which would make the day the hottest on record in more than a decade. Meanwhile, Washington D.C. and Baltimore are nearing all-time highs, with temperatures expected to reach 111 degrees.

Meteorologists expect extreme conditions to persist during the July 4 weekend, one of the dates with the greatest mobility and outdoor activities in the United States. In addition to high daytime temperatures, nights will remain unusually warm, with lows above 79 degrees Fahrenheit in several cities, reducing the body's ability to recover from heat stress.

The National Meteorological Service warned that “the dangerous heat will continue for several days in large areas of the center and east of the country,” so it urged the population to stay hydrated, avoid strenuous activities during the hours of greatest solar radiation and go to air-conditioned spaces when possible.

Pressure on the electrical network

The extraordinary demand for electricity to power millions of air conditioning systems has also set off alarm bells among energy authorities.

The United States Department of Energy issued an emergency order for the operator PJM Interconnection, the largest electrical grid in the country, which supplies 13 states and the District of Columbia, with the aim of guaranteeing electricity supply and avoiding blackouts during peak consumption. As part of the measures, Energy Secretary Chris Wright instructed large electricity consumers, including data centers, to use their backup generators when necessary to reduce the load on the grid.

The decision responds to demand forecasts close to historical highs, driven by the massive use of cooling systems in the midst of the extreme heat episode. Electrical companies from various states have also asked the population to reduce energy consumption during peak demand hours to preserve the stability of the system.