Weather can be an important feature in history. On the evening of December 25th into the 26th in 1776, George Washington crossed the ice choked Delaware River. That action was the first move in a surprise attack against the German Hessian allied mercenary forces at Trenton, New Jersey, in the Battle of Trenton on the morning of December 26. The march on Trenton occurred in the midst of snow and sleet. The combination of the holiday season and unfavorable weather resulted in the surprise and capture of many of the garrison, and is said to mark a turning point in the American Revolution.
Mary Knapp, Weather Data Library