The winter of 1783-1784. The Revolutionary War had just ended, and Benjamin Franklin was puzzling over the nation's bizarre weather. Congress had been delayed getting to Annapolis to vote for the Treaty of Paris because the Chesapeake Bay just wouldn't melt. The Mississippi River froze down to New Orleans, and ice was reported floating in the Gulf of Mexico. Reports from Europe were of a bizarrely hot summer with thick fog that was choking people to death in Scotland, massive hailstones, lightning, and crop failures. The sun was blood-red at noon. Mass starvation that would ultimately kill 1/6ths of Egypt's population took hold due to a historic drought of the Nile. As many as six million people would die from the bizarre weather.
Franklin was one of the few scientists of the era to (almost) correctly speculate as to its cause:
"The cause of this universal fog is not yet ascertained [...] or whether it was the vast quantity of smoke, long continuing, to issue during the summer from Hekla in Iceland, and that other volcano which arose out of the sea near that island, which smoke might be spread by various winds, over the northern part of the world, is yet uncertain."
He, however, had mixed up his Icelandic volcanoes, for it was not Hekla that erupted that year, causing the planet-altering weather, but Laki (Eldgjá). A rift 23 kilometers long opened up in places up to 100 meters wide with lava fountains at times reaching over a kilometers into the air - and it continued erupting for 8 months.