A heat dome — a high-pressure system above a region that traps heat and humidity — has been smothering parts of the U.S., from the Midwest to the East Coast.

Multiday warnings of extreme heat have landed in New York, Boston and Philadelphia. The sultry weather has pushed east just ahead of weekend Fourth of July events in a region that…

Multiday warnings of extreme heat landed in New York, Boston and Philadelphia on Wednesday as sultry weather pushed east just ahead of Fourth of July celebratio