volcanic winter of 536
A volcanic eruption, possibly in El Salvador, Iceland, or somewhere in North America, is believed to have caused a volcanic winter beginning in 536. Most of the documentation of this event comes from Constantinople, even though its impact was felt well beyond Europe. Temperatures fell about 2.5° below normal, and another eruption in 539–540 extended the volcanic winter and sent temperatures 2.7° below normal. Crop failures were widespread, the sun was sapped of strength, and wintry weather was experienced well outside the bounds of winter (e.g. snow fell in China in August).
For Europe in particular, this volcanic eruption marked the beginning of a very difficult time, as it was followed in 541 by the Plague of Justinian.