New England's Dark Day occurred on May 19, 1780, when an unusual darkening of the daytime sky was observed over the New England states and parts of eastern Canada. The primary cause of the event is believed to have been a combination of smoke from forest fires, a thick fog, and cloud cover.

On May 19, 1780, the skies over New England and New York darkened for a full day. In the preceding days, the sun and moon had appeared red-tinted, and by noon of May 19, the sky was nearly dark as night. It was known as The Dark Day.  One contemporary observer wrote, The extent of this darkness was very remarkable &.