In the summer of 1816, the Northern Hemisphere was plagued by a weather disruption of seemingly biblical proportions. Following a relatively ordinary early spring, temperatures in the eastern United States plunged back below freezing, and communities from New England to Virginia experienced heavy snowfalls and crop-killing frost during June, July and August. Europe also found itself in the grip of an unseasonable chill. Winter snows refused to melt, and between April and September, some parts of the Continent were drenched by as many as many as 130 days of rain. The unrelenting gloom inspired author Mary Shelley to write her famous novel “Frankenstein,” but it also wreaked havoc on farmers. Crops failed across Europe and China, spawning deadly famines and outbreaks of typhus and other diseases. In India, the disturbances gave rise to a virulent new strain of cholera that eventually killed millions. The suffering in the United States was less pronounced, but many still felt the squeeze of soaring grain prices. Some poorer Americans were even reduced to eating hedgehogs and scrounging for wild turnips.

What caused this calamitous “Year Without a Summer?” At the time, many people believed the chaos was some form of divine retribution, but most scientists now place the lion’s share of the blame on an Indonesian volcano called Mount Tambora. In early 1815, Tambora roared to life with one of the most devastating volcanic eruptions on record—an explosion 10 times more powerful than Krakatoa. Along with killing thousands of locals, the blast also spewed sulfur dioxide into the stratosphere. The ash cloud drifted across the globe in the months that followed, blotting out the sun and creating a volcanic winter. When combined with the lingering effects of the Little Ice Age—a period of global cooling that lasted from the 14th to 19th centuries—the sun-sapping pall was enough to lower the planet’s average temperature and send weather patterns into a tailspin.