Throughout history, odd natural phenomena have occurred that exceeded our horizon of understanding. Many times the unknown spurred more questions than answers, often leaving any possible explanations up to interpretation.
One such example of this occurred on May 19, 1780 in New England, when the daytime sky darkened enough that candles were needed during the afternoon in order to continue daytime work.
The Darkened Day
In the days leading up to the event, the sun over New England appeared red and the sky carried a yellowish hue. This reddish tinting continued into the overnight hours when the moon was also observed to be red.
Areas further to the north began to report the darkness earlier than their counterparts further south, with the sky already darkened in southern Vermont by sunrise. As the morning progressed, so did the darkness, being seen in eastern Massachusetts where observers at Harvard University reported the first arrival by mid-morning, peaking shortly after noon, and subsiding into the early afternoon. After the darkness, Harvard reported overcast skies for the remainder of the day. Elsewhere in Massachusetts, where rain began to develop, a light film of ash and burned leaves topped puddling water.
A first hand report from Revolutionary War soldier Joseph Plumb Martin notes how the darkness impacted the natural day-night cycle animals followed, with roosters crowing and fowls going back to their roosts.
Explanations from the Period
The late 18th century was a period where old superstitions and the modern developments of the Enlightenment meshed to try and explain the unknown. In colonial New England, where Puritan beliefs were the fundamental bedrock of society, the odd dark day was seen as a religious omen, indicative that the end times were near.
Current Theories on the Possible Causes
The actual cause of the New England Dark Day of 1780 is likely a result of extensive forest fires that produced enough smoke to obscure the skies. Researchers in Canada have examined tree rings and have identified scars that would date back to approximately 1780, further bringing credence to the theory. Given the untouched expanse of the continent at that time, with most European settlement hugging the coast, it is likely that fires deeper inland would have been unknown to faraway observers.
Coupling the likely smoke from forest fires with the known conditions on the day, it is possible the exceptionally dark skies were exacerbated by fog and cloud cover as rainfall developed in the region. This unique combination of events, combined with the mindset of the time period, helped cement this unique day in the weather history book.