Overview
- A persistent upper‑level heat dome has driven widespread Extreme Heat Warnings and Heat Advisories across much of the Midwest, Mid‑Atlantic and Northeast, producing heat‑index values commonly between 100°F and 115°F.
- Thursday saw many cities hit near‑record highs, with Boston reaching 100°F and other reporting centers recording daily records and unusually warm overnight lows that limit nighttime relief.
- Public‑health officials and cardiologists warned that the heat raises heart and cardiovascular strain, urged hydration and shade, and opened cooling centers while utilities and transit agencies prepared for higher electricity use and service impacts.
- Forecast models show the ridge beginning to weaken late Friday, which will increase the chance of thunderstorms—some potentially strong with damaging wind and hail—before humidity and temperatures fall toward Sunday and early next week.
- Climate experts link the severity and scope of the event to long‑term warming and the current El Niño pattern, and officials say vulnerable groups without reliable cooling remain at highest risk during the holiday period.