The 2014–15 North American winter was frigid and prolifically wintry, especially across the eastern half of North America in the months of January–March. The season began early, with many places in North America experiencing their first wintry weather during mid-November. A period of below-average temperatures affected much of the contiguous United States, and several records were broken. A quasi-permanent phenomenon referred to as the polar vortex may have been partly responsible for the cold weather. Temperatures in much of the United States dropped below average by November 19, following a southward "dip" of the polar vortex into the eastern two-thirds of the country. The effects of this dip were widespread, bringing about temperatures as low as in Pensacola, Florida. Following a significant snowstorm there, Buffalo, New York received several feet of snow from November 17–21. In addition, significant winter weather occurred throughout the season, including a major blizzard that struck the Northeastern United States at the end of January, another blizzard that affected much of the Northern United States days later in early February, and several significant snow events paired with very frigid temperatures for much of February.
Many records for snowfall and temperature were broken, many for the month of February, with every state east of the Mississippi River being colder than average, some for the entire winter. However, this meteorological winter was the 19th-warmest of the past 120 winters over the Contiguous United States, largely due to persistent warm weather in the Western United States. During the 2014–15 winter season, Boston broke its all-time official seasonal snowfall record from the winter of 1995–96, with a total snowfall record of as of March 15, 2015. An early trace of snowfall was recorded in Arkansas. There were greater accumulations of snow across parts of Oklahoma as well.
While there is no well-agreed-upon date used to indicate the start of winter in the Northern Hemisphere, there are two definitions of winter which may be used. Based on the astronomical definition, winter begins at the winter solstice, which in 2014 occurred on December 21, and ends at the March equinox, which in 2015 occurred on March 20. Based on the meteorological definition, the first day of winter is December 1 and the last day February 28. Both definitions involve a period of approximately three months, with some variability.
Seasonal forecasts
On October 16, 2014, the National Oceanic and Atmospheric Administration's Climate Prediction Center issued its U.S. Winter Outlook. This outlook indicated that below-average temperatures in parts of the south-central and southeastern United States would be favored, with above-average temperatures favored in the western U.S., Alaska, Hawaii, and New England. Drought conditions were expected to improve in California's southern and northwestern regions, but no improvements were expected earlier than December or January. Above-average conditions were also expected to pervade the winter months in the western U.S., the Intermountain West extending across the U.S.–Canada border through New York and New England, and Alaska and Hawaii. The Precipitation Outlook favored above-average precipitation across the southern tier and Atlantic coast of the United States, with above-average precipitation also favored in southern Alaska and the Alaska panhandle. Below-average precipitation was favored in Hawaii, the northwestern United States, and near the Great Lakes region. The rest of the country was given an "equal chance" for either above- or below-average temperatures and/or precipitation.
On November 30, 2014, Environment Canada's monthly prediction system produced a forecast for the months of December, January, and February across Canada. Areas in and just off the western coast of British Columbia were considered the most likely areas for above-average temperatures. Other areas where above-average temperatures were favored by the forecast included Yukon, the Northwest Territories, northern parts of Alberta and Saskatchewan, and northwestern parts of Manitoba. Below-average temperatures were favored in and near Lake Superior in Ontario, across much of Hudson Bay, in far-eastern parts of Nunavut, and in northern parts of Quebec. The most favorable locations for above-average precipitation were northwestern British Columbia, southwestern Yukon, eastern parts of the Northwest Territories, western parts of Nunavut, and Newfoundland. The most favorable areas for below-average precipitation were southeastern British Columbia, southern Alberta, southern Saskatchewan, some northern parts of Quebec, and an isolated spot in the northern half of Nunavut.
Seasonal summary
The North American winter season of 2014–15 expressed a significant level of variance. First, a cyclone in the Bering Sea enabled a change in the atmospheric pattern to occur; according to Jeff Masters from Weather Underground, this cyclone brought about a "ripple" in the jet stream, and the presence of a high-pressure ridge over the western United States and a low-pressure trough over the southern and central United States enabled a great intrusion of very cold air to pervade southward out of Canada. Following the onset of the cold wave, multiple snow events occurred; one significant storm dropped as much as of snow in a single area, and impacts covered a broad area. In late November, around Thanksgiving, a nor'easter traveled up the East Coast, dropping up to a foot of snow in some areas, and causing major travel headaches for much of the country. Due to the storm, over 4,500 flights were canceled and over 400,000 people were without power on November 27; southern New Hampshire was the worst hit, experiencing up to 200,000 outages. December was, at the time, the second warmest across the US.December 2014 National Climate Report, NOAA However, 2015, 2021 and 2023 have since had warmer Decembers, leaving 2014 in fifth.December 2015 National Climate Report, NOAADecember 2021 National Climate Report, NOAADecember 2023 National Climate Report, NOAA In December, yet another storm impacted parts of North America; the storm brought relief to drought-stricken parts of California, but it also brought dangerous mudflows to fire-ravaged areas where the soil could not handle the excess precipitation. Less than two weeks after this event, another storm impacted the Pacific coast of the United States; this storm, fueled by the "Pineapple Express", knocked out power to over one hundred thousand customers in the San Francisco Bay Area after producing strong winds. Hurricane-force winds were reported in parts of the northwestern United States. Regions reported as much as of rainfall, and parts of the Sierra Nevada reported of snowfall.
Due to a persistent stationary high-pressure pattern over the west coast that redirects the jet stream, it remained (and remains) in a wavy ideal configuration to bring warm air north over the western U.S. and cold air towards the south over the continental states, and to favor winter storms over the East Coast. Severe winter blizzards over New England are often associated with this configuration, and nearly all of the snow storms this season followed very similar tracks and had marked similarities in their synoptic evolution. Boston in particular saw the effects of this, experiencing six major snow storms in the first two months of the year, leaving it with over of snow. January 27 saw first major snowfall of 2015, with observations showing a blocked flow with warm air over the west coast, accompanied by a pronounced cold trough downstream, which pattern looks very similar to the blizzard that Boston saw on January 23, 2005.
As a result, February was record-breaking for many cities in the United States, yet in opposite extremes. Much of February saw below-average cold in the eastern part of the country, it was markedly warm in the West. A multitude of cities east of the Mississippi experienced their coldest February in decades, including Chicago, Ill.; Cleveland, Oh.; Grand Rapids, Mich.; Harrisburg, Pa.; Hartford, Conn.; and Portland, Maine. Marquette, Mich. Syracuse, Buffalo and Rochester, N.Y. also set records for coldest month overall, as did Bangor, Maine where the average temperature was . And with an average temperature of , the state of Maine itself also set a record low. For Worcester, Mass, February was the coldest month out of any month on record with an average temperature of just , while also accumulating more than of snow this winter.
In contrast, in the West a persistently strong ridge of high pressure over the warm eastern Pacific Ocean and western North America elevated temperatures to record levels from Arizona to Washington. It was the warmest winter month (December, January, February) on record in San Francisco; Seattle; Portland, Ore.; Reno, Nev.; Las Vegas; and Salt Lake City, with the latter realizing an average temperature for February of , breaking the old record set in 1907. Meanwhile, just of snow fell in the entire month in Anchorage, Alaska, making it the fifth-least-snowy February on record.
Portland and Salem had their warmest February on record, with the latter tying the record set in 1934 for their warmest at degrees with the year. For the first time in record keeping, every day in February was at least in Salem.
California averaged warmer than the previous warmest winter (2013–14), which had broken the previous record (1980–81) by . February was the warmest on record in Washington, California, Utah and Arizona, while February was among the top 10 warmest in four other states. Overall, the National Oceanic and Atmospheric Administration reported that about 30.6 percent of the country was "very warm" – meaning February was in the warmest 10 percent of the historical record – while 31.5 percent of the country was "very cold," or in the coldest 10 percent historically.
Events
There were several winter weather events during the 2014–15 North American winter. Significant events include cold waves, snowstorms, and other notable events outside the conventional limits of winter.
November Bering Sea cyclone
In early November 2014, Typhoon Nuri peaked in intensity as a Category 5-equivalent typhoon on the Saffir–Simpson hurricane wind scale. The storm became extratropical on November 8, and it was absorbed by a new center of circulation. The new, more powerful cyclone entered the Bering Sea, and intensified to become the most powerful storm to ever impact the region, with a minimum barometric pressure of . This compares to the previous record of from a storm on October 25, 1977. In association with the storm, there were winds exceeding hurricane-force with a wind gust of recorded at Shemya, Alaska. The storm also produced waves as high as , although waves were lesser on the Alaska coast. The storm weakened as it moved westward, and it produced a "ripple" in the jet stream which allowed for a strong cold front to dive southward out of Canada into the United States, producing a cold wave.
November cold wave