Heat wave to hit U.S. East ahead of July 4, Washington nears 40 C
2026-06-30
The U.S. National Weather Service (NWS) on Thursday forecast a dangerous heat wave spreading across the U.S. Midwest and East. Temperatures are rising ahead of the July 4 Independence Day holiday, with Washington, D.C. expected to reach a high of about 40 C. A so-called heat dome, which traps warm air aloft, is seen as the cause.
Above 38 C in the U.S. East
According to the weather service, highs are expected to exceed 38 C over a wide area on July 3-4, including Washington, New York City and Philadelphia in eastern Pennsylvania. Humidity will also be high, and the feels-like temperature could top 40 C in many areas.
Impact on Independence Day events
In the United States, events tied to Independence Day and the nation's 250th anniversary are scheduled in Washington, Philadelphia and other cities, along with matches in the knockout stage of the FIFA World Cup. The weather service warned that people who are not staying hydrated or taking cooling measures could suffer health problems, and urged caution over heatstroke. Forecasts show that this intense heat could put more than 180 million people at risk of serious health effects. The heat is expected to gradually ease after July 5.
Heat domes and climate change
A heat dome is a phenomenon in which high pressure systems that develop aloft trap warm air near the surface, raising temperatures across a wide area. When the high pressure system stalls, extreme heat can last from several days to several weeks.
The phenomenon has caused severe damage in North America before. In late June 2021 in western North America, temperatures above 40 C were recorded in places including Oregon, Washington state and British Columbia in western Canada, and more than 600 people died in the United States and Canada. Infrastructure was also affected, with heat warping roads and railway wires.
The impact of heat domes is also spreading in Europe. In France, intense heat above 40 C has continued in many areas since June, and the French public health agency said excess deaths in the country since June 24 have reached about 1,000. According to Reuters, record high temperatures were broken in Austria, the Czech Republic, Germany and Poland.
Climate change has been cited as a factor behind the succession of heat waves. World Weather Attribution (WWA), an international group that analyzes the link between climate change and extreme weather, said Europe's heat wave could not have occurred without climate change, calling it 'the most severe on record.' Global warming is pushing temperatures higher and increasing the frequency of heat waves around the world.
Enjoyed this article? Share it with your network!