Backdoor cold front
A backdoor cold front, or backdoor front, is a cold front moving south or southwest along the northeast of the Atlantic seaboard in North America, particularly in the New England region of United States and the Great Lakes. Typically occurring in spring, the front drives cool Atlantic air from the east or northeast into northeastern US that supersedes the warmer continental air. The front is termed "backdoor" because it arrives from the east, meaning it originates from the opposite direction of a typical cold front and therefore comes through the region's "back door."
Formation
A backdoor cold front occurs when the clockwise motion around a high-pressure system pulls in colder air toward the south and west of it. This is where a synoptic wind motion creates a wind flow from the cool North Atlantic Ocean that brings in the backdoor front. A cold front, however, approaches from the north, northwest or west, and its wind direction will generally be from those directions, except this does not happen with a backdoor cold front. Rather, a back door cold front arrives from a particular direction, where it will move in an opposite direction, unlike a regular cold front.In spring, the Atlantic ocean is still cool, and hence the air above it is also cool. On occasion, that air can move south out of high pressure area in the Canadian Maritimes and southward down the New England coast or the northern states. The high pressure system's clockwise flow directs cold moist air southward and westward into Northeast US. The area where these two airmasses collide is illustrated by the frontal boundary in Northern New England and northern New Jersey. Low clouds develop along and behind the front. As a backdoor cold front withdraws, temperatures can rise rapidly.
Characteristics
Backdoor fronts would point toward the southeast direction, but they can alter, such as an east–west emplacement or may move towards the northeast if the cold front is encircling a subtropical cyclone. The leading boundary of this cold air forms a cold front, which is typically represented on surface analysis charts as a front aligned roughly east-west. The backdoor cold front may move towards the southwest or west. Heatwaves are frequently ended by a backdoor front – This is when temperatures are around, which is warm for May standards, whereby the front will lower the temperature down to around by the next day.During the spring months, when ocean temperatures of the Atlantic Ocean are still cool, backdoor fronts can drop temperatures by more than in just a few hours, because their force is assisted by the cool, oceanic air mass that lies over the cool north Atlantic waters. They are mostly shallow, with much of the maritime air only reaching a few thousand feet aboveground and thus would rarely pass the over the Appalachian Mountains. The clouds associated with the backdoor cold front stretch from southern Illinois to North Carolina. Low clouds develop along and behind the front because such the front's winds usually come from the ocean, in addition to scattered showers, although the precipitation is mist and drizzle. Its effects may last a few hours or a couple of days, depending on the system.
Areas affected
Back door cold fronts are common from southeast Canada to New Jersey, due to cool Atlantic water lingering near the coast in spring. They normally impact southeastern Canada, the New England coast, south to the New Jersey coast. New York City feels the effects of backdoor cold fronts much less than Boston. The warm Gulf Stream prevents the cool onshore flow of the front, so regions from southeast Virginia southward are typically not impacted by backdoor cold fronts. Backdoor fronts can create contrasting temperatures between the seaboard and inland areas in spring and early summer – For instance, Boston may experience cloudy skies with temperatures hovering between, while Trenton, New Jersey, which is around to the southwest, might experience mild and sunny conditions with temperatures near .Notable examples
On May 27, 2014, a backdoor cold front from southeast Canada came down the New England coast. Boston struggled to reach, when it was two days earlier. Worcester set a record low-maximum on the May 28 when it had a high of, which was below the average high of. In New York City, after reaching a high of on May 27, the high only reached the next day after the front passed. Between May 28 and 29, maximum temperatures dropped from to at Harrisburg, Pennsylvania and from down to in Washington, DC.On March 29, 2025, after a warm front had moved northeast past New York city earlier in the day, the same front moved back southwest as a backdoor cold front later in the afternoon. Notable temperature drops were from to degrees in five minutes at Laguardia Airport, to in ten minutes at Hofstra University, and to in one hour at Central Park.