Overview
- As of Tuesday, June 30, the National Weather Service has placed large areas under Extreme Heat Watches and Warnings with more than 74 million people under heat alerts and roughly 180 million in the highest ‘major’ or ‘extreme’ heat‑risk categories.
- Forecasters say the heat will peak mid‑week into the July 4 holiday, with daytime temperatures in the 90s to low 100s F and heat‑index (feels‑like) values reaching 105–115°F in some areas, while overnight lows will often remain in the 70s and offer little relief.
- Local governments and agencies have begun cancelling or modifying outdoor events, opening cooling centers, deploying heat‑patrols and adding medical resources to protect vulnerable groups such as the elderly, young children, the unhoused and people without air conditioning.
- The prolonged, humid heat raises the risk of heat illness, could increase emergency room visits, threaten power and water systems during high demand, and is expected to challenge or break many daily high‑temperature and record‑warm overnight lows.
- Meteorologists say a stationary heat dome — a strong ridge of high pressure — is causing the pattern, with limited, uncertain relief possible from scattered thunderstorms and a weakening ridge later in the holiday weekend.