Cape Cod - Climate

Climate

Although Cape Cod's weather is typically more moderate than inland locations, there have been occasions where Cape Cod has dealt with the brunt of extreme weather situations (such as the Blizzard of 2005 and Hurricane Bob). Because of the influence of the Atlantic Ocean, temperatures are typically a few degrees cooler in the summer and a few degrees warmer in the winter. A common misconception is that the climate is influenced largely by the warm Gulf Stream current; however, that current turns eastward off the coast of Virginia, and the waters off the Cape are more influenced by the cold Canadian Labrador Current. As a result, the ocean temperature rarely gets above 65 °F (18 °C), except along the shallow west coast of the Upper Cape.

The Cape's climate is also notorious for a delayed spring season, being surrounded by an ocean which is still cold from the winter; however, it is also known for an exceptionally mild fall season (Indian summer), thanks to the ocean remaining warm from the summer. The highest temperature ever recorded on Cape Cod was 104 °F (40 °C) in Provincetown, and the lowest temperature ever was −12 °F (−24 °C) in Barnstable.

The water surrounding Cape Cod moderates winter temperatures nearly enough to extend the humid subtropical climate zone to what could be its northernmost limit in eastern North America. Consequently, many subtropical indicator plant species typically found in more southerly latitudes grow there, including Camellias, Ilex opaca, Magnolia grandiflora and Albizia julibrissin. However, Cape Cod falls below the 32 degree threshold as the coldest month, January, averages around 30-31 (depending on exact location), with the true climate being either a maritime climate or a humid continental climate (particularly on the northern coast of the upper and mid cape, which is somewhat sheltered from the cooler onshore wind to the south).

Precipitation on Cape Cod and the islands of Martha's Vineyard and Nantucket is the lowest in the New England region, averaging slightly less than 40 inches (1,000 mm) a year (most parts of New England average 42 to 46 inches (1,100 to 1,200 mm)). This is due to storm systems which move across western areas, building up in mountainous regions, and dissipating before reaching the coast where the land has leveled out. The region does not experience a greater number of sunny days, however, as the number of cloudy days is the same as inland locales, in addition to increased fog. On average, 24 inches (610 mm) of snow, which is 18 inches (460 mm) less than Boston, falls in an average winter.

Tropical storms occasionally strike the Cape. Once every five or six years, a tropical storm, accompanied by very high and potentially damaging winds and heavy rain, will strike the region. About once every 11 or 12 years a hurricane brings damaging winds and storm surges to the region. Several Category 3 storms have struck Cape Cod since record-keeping began, such as the Long Island Express of 1938 and the 1944 Great Atlantic hurricane. Strong Category 2 storms, such as Hurricane Carol of 1954 and Hurricane Bob of 1991 also caused considerable damage. Notable Catgory 1 storms include Hurricane Edna of 1954 (shortly following Hurricane Carol) and Hurricane Donna of 1960. Other notable storms include the Gale of 1815 (most likely itself a strong hurricane, though at the time, measuring strength and assigning a catgory was not possible) and the 1991 Perfect Storm on October 31, 1991.