The February 2015 North American cold wave was an extreme weather event that affected most of Canada and the eastern half of the United States. Following an earlier cold wave in the winter, the period of below-average temperatures contributed to an already unusually cold winter for the Eastern U.S. Several places broke their records for their coldest February on record, while some areas came very close. The cause of the cold wave was due to the polar vortex advancing southward into the eastern parts of the U.S, and even making it as far south as the Southeast, where large snow falls are rare. By the beginning of March, although the pattern did continue for the first week, it abated and retreated near the official end of the winter.
In addition to the extremely cold weather, multiple winter storms affected nearly the entire United States, especially in the snow-weary Northeast, which had already seen nearly of snow in the latter part of January; this was added to by roughly more snow, leading to Boston having its highest seasonal snowfall on record.
Origins
Like most American cold waves, this was caused by the southward movement of the polar vortex into the United States due to changes in the jet stream in early February 2015. However, unlike most which last for a few days, this one remained for much of the entire month. This was partly due to the Ridiculously Resilient Ridge, which persisted over parts of Alaska for much of the month, essentially keeping the jet stream pattern "locked" for several weeks. This allowed for bitterly cold air masses to migrate southward into the eastern part of the country, leading to well-below average temperatures.
Record temperatures
United States
The average temperature in Boston for January was below the 1981–2010 normal, and the average temperature in February was , which was below the 1981–2010 normal, making it the second-coldest month of any month all-time, behind February 1934. March was below average. By the end of a period spanning from the beginning of February to the end of December, Worcester, Massachusetts, saw a record of snowfall, breaking the record set in 2004–05, which was over the average. Hartford, Connecticut, and Providence, Rhode Island, saw similar below-average temperatures for the two months, with Hartford's February finish of besting February 1934 to become the coldest month of any month all-time in record keeping.
The average temperature in Bangor, Maine, for February was , about below normal, breaking the old record of set in January 1994. Portland, Maine, also saw a record coldest average monthly temperature of in February. On February 24, 2015, the temperature at Dulles International Airport in Northern Virginia dipped to , breaking the previous daily record of set in 1967 (but not the all-time low at the airport of -18 °F or -28 °C set on January 22, 1984).
Rutland, Vermont, saw a record averaged cold for February of , breaking its previous record of set in 1934. Montpelier, Vermont, realized its coldest February with an average temperature of , below the 1979 record of .
The average February temperature in Syracuse, New York, was degrees below normal at , breaking by 3 degrees the record set in February 1934. They saw a record 25 days below . Ithaca, New York also had its coldest month in record keeping with an average temperature of . While New York City didn't have its coldest February on record, the average temperature of was still its 3rd coldest. Only one day, February 20, set daily records for cold, at . However, one of the NWS New York reporting sites, Islip, did see their coldest month on record, with a mean temperature of . JFK International Airport realized its coldest February and second coldest month on record as well, with a temperature of . However, records don't go back as far as they do in Central Park.
The average temperature in Buffalo, New York, set a record in February for its all-time coldest month with an average temperature of . breaking the prior record set in 1934 of . Before that, the previous coldest February was in 1875 with an average temperature of . It was also the second time in history that the entire month of February was below freezing. Other cities that broke cold weather records for February included Cleveland, at , while Chicago tied its February 1875 record at . Rochester, New York, also set a record for coldest month overall.