page_title: Boston
section_title: Climate
hierarchical_section_title: Boston / Geography / Climate
caption_attribution_description: English: A graph of cumulative snowfall in Logan International Airport in Boston, Massachusetts since 1938.
context_page_description: Boston is the capital and most populous city of the Commonwealth of Massachusetts in the United States, and the 21st most populous city in the United States. The city proper covers 49 square miles with an estimated population of 692,600 in 2019, also making it the most populous city in New England, and is the seat of Suffolk County. The city is the economic and cultural anchor of a substantially larger metropolitan area known as Greater Boston, a metropolitan statistical area home to a census-estimated 4.8 million people in 2016 and ranking as the tenth-largest such area in the country. As a combined statistical area, this wider commuting region is home to some 8.2 million people, making it the sixth most populous in the United States.
  Boston is one of the oldest municipalities in the United States, founded on the Shawmut Peninsula in 1630 by Puritan settlers from the English town of the same name. It was the scene of several key events of the American Revolution, such as the Boston Massacre, the Boston Tea Party, the Battle of Bunker Hill, and the Siege of Boston.
context_section_description: Under the Köppen climate classification, depending on the isotherm used, Boston has either a humid subtropical climate (Köppen Cfa) under the −3 °C (26.6 °F) isotherm or a humid continental climate under the 0 °C isotherm (Köppen Dfa). The city is best described as being in a transitional zone between the two climates. Summers are typically hot and humid, while winters are cold and stormy, with occasional periods of heavy snow. Spring and fall are usually cool to mild, with varying conditions dependent on wind direction and jet stream positioning. Prevailing wind patterns that blow offshore minimize the influence of the Atlantic Ocean. However, in winter areas near the immediate coast will often see more rain than snow as warm air is drawn off the Atlantic at times. The city lies at the transition between USDA plant hardiness zones 6b (most of the city) and 7a (Downtown, South Boston, and East Boston neighborhoods).
  The hottest month is July, with a mean temperature of 73.4 °F (23.0 °C). The coldest month is January, with a mean of 29.0 °F (−1.7 °C). Periods exceeding 90 °F (32 °C) in summer and below freezing in winter are not uncommon but rarely extended, with about 13 and 25 days per year seeing each, respectively. The most recent sub-0 °F (−18 °C) reading occurred on January 7, 2018, when the temperature dipped down to −2 °F (−19 °C). In addition, several decades may pass between 100 °F (38 °C) readings, with the most recent such occurrence on July 22, 2011, when the temperature reached 103 °F (39 °C). The city's average window for freezing temperatures is November 9 through April 5. Official temperature records have ranged from −18 °F (−28 °C) on February 9, 1934, up to 104 °F (40 °C) on July 4, 1911. The record cold daily maximum is 2 °F (−17 °C) on December 30, 1917 while, conversely, the record warm daily minimum is 83 °F (28 °C) on August 2, 1975 and July 21, 2019.
  Boston's coastal location on the North Atlantic moderates its temperature but makes the city very prone to Nor'easter weather systems that can produce much snow and rain. The city averages 43.8 inches (1,110 mm) of precipitation a year, with 43.8 inches (111 cm) of snowfall per season. Most snowfall occurs from mid-November through early April, and snow is rare in May and October. There is also high year-to-year variability in snowfall; for instance, the winter of 2011–12 saw only 9.3 in (23.6 cm) of accumulating snow, but the previous winter, the corresponding figure was 81.0 in (2.06 m).
  Fog is fairly common, particularly in spring and early summer. Due to its location along the North Atlantic, the city often receives sea breezes, especially in the late spring, when water temperatures are still quite cold and temperatures at the coast can be more than 20 °F (11 °C) colder than a few miles inland, sometimes dropping by that amount near midday.
  Thunderstorms occur from May to September, that are occasionally severe with large hail, damaging winds and heavy downpours. Although downtown Boston has never been struck by a violent tornado, the city itself has experienced many tornado warnings. Damaging storms are more common to areas north, west, and northwest of the city. Boston has a relatively sunny climate for a coastal city at its latitude, averaging over 2,600 hours of sunshine per annum.
caption: A graph of cumulative winter snowfall at Logan International Airport from 1938–2015. The four winters with the greatest amount of snowfall are highlighted. The snowfall data, which was collected by NOAA, is from the weather station at the airport.
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