The cloud spread around the world and caused global temperatures to drop 2 degrees Celsius, or about 3 degrees Fahrenheit. That doesn’t sound like much of a change, but in fact, it’s a massive change, and it caused the Year Without Summer in 1816, and it stayed abnormally cool for almost a decade. Crops failed, people starved and rioted, diseases ran rampant, rivers froze. April was cruel; A snowstorm started on April 12 that buried Quebec City in four feet of snow. That was just the start. In August, Thomas Jefferson wrote: “We have had the most extraordinary year of drought and cold ever known in the history of America.”