Weather is history. Storms are woven into our national stories as much as battles and revolutions or trials and triumphs. The powerful blow of a hurricane or tragic spark of a wildfire can raze neighbourhoods and form community bonds that last for generations.

But for all the disasters that dot our historical landscape, there are just as many significant events that were silently driven by weather conditions that wound up changing the world.

DON’T MISS: Do you love weather and history? Every episode of This Day in Weather History is now available—check it out!

September 11, 2001

Every recounting of the horror of the attacks on September 11, 2001, starts with a description of the crystal clear skies that blanketed the U.S. East Coast that morning.

History is so full of torrential storms that 9/11 stands out as one of the few instances where so many people remember a complete lack of active weather. The sky was a stunning shade of blue that Tuesday.

A potent cold front swept through the eastern U.S. the night of September 10th, bringing the region its first taste of fall after a long, hot summer. The front triggered rain and thunderstorms the night before, with low clouds and poor visibility throughout the Interstate 95 corridor.

The timing of the cold front changed the course of world history. If it had come through a little bit slower, the weather that Tuesday morning may have caused flight delays or cancellations that would’ve…