Half of all Americans are facing prolonged, dangerously hot temperatures from an intense heat dome as they head outdoors to celebrate the country’s 250th Independence Day.

The temperatures in some spots in the eastern US, like New York City and Washington, DC, could be the hottest in over a decade, and numerous high temperature records are likely to fall in the coming days.

The oppressive heat and humidity are already gripping the Midwest and South and it will expand to the Mid-Atlantic and Northeast on Wednesday. The sprawling heat dome will then park over the East, particularly the Interstate 95 corridor, and peak by Friday.

Many areas will endure consecutive days of temperatures in the mid-90s to low 100s. Humidity will make it feel even hotter and make it harder to cool down — pushing “feels like” temperatures as high as 110 degrees or more.

Heat waves worldwide are becoming more harsh and frequent because of human-caused warming from fossil fuel pollution. The record-shattering heat waves in Europe last week and in the western US in March are two recent examples.