America’s 250th birthday celebration was supposed to be one of the biggest events in the nation’s history. Instead, record-breaking heat, dangerous thunderstorms, emergency evacuations, and severe weather forced officials to cancel parades, alter major events, and protect hundreds of thousands of people from life-threatening conditions.

Discover how a powerful heat dome sent temperatures soaring above 100°F across the Mid-Atlantic, why the heat index climbed well above 110°F, and how the atmosphere produced severe thunderstorms capable of disrupting celebrations on the National Mall just hours later.

We also explore why extreme heat remains America’s deadliest weather hazard, how emergency managers prepared for millions of visitors, what happens to power grids, transportation systems, and infrastructure during prolonged heat waves, an ...