Winter of 2012 Named 4th-Warmest for US

For many living in the lower 48 states, winter felt unusually warm. Now, it's official.

Today, March 7, the U.S. National Climatic Data Center named this winter — collectively December, January and February — the fourth-warmest for the lower 48 states since record-keeping began more than a century ago. The record for the warmest winter remains with 2000.

Above-average temperatures were most notable in the Northern Plains, Midwest, Southeast and Northeast, according to the Center. Twenty-seven states had winter temperatures that ranked among their 10 warmest. New Mexico was the only state that had winter temperatures below the 20th-century average.

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In spite of record cold in January, the rest of the winter was kinder to Alaska, bringing the state to just below its seasonal average. (Because Alaska is outside the lower 48 states, its data did not figure into the 4th-warmest ranking.) [6 Signs Spring Has Sprung]

Precipitation was low overall, too, particularly in the West. Most notably, California had its second-driest winter on record. The central U.S., however, had more precipitation than usual.

Meteorologists have attributed the unusually mild weather in much of the United States and southern Canada to the behavior of high-altitude westerly winds called the jet stream. The polar branch of the jet stream has kept cold, Arctic air bottled up farther north than usual. A break in this pattern resulted in the frigid spell centered on Eastern Europe beginning in late January; North America, however, was not affected.

While this unusually mild winter weather may bring to mind global warming, climate scientists are loath to directly connect short-term weather, even over the course of a season, with much longer-term shifts in climate.

Even so, they say, this strangely warm winter isn't coming out of the blue; the planet has been warming up steadily. For instance, the last decade that began in 2000 was the warmest on record for more than a century.

You can follow LiveScience senior writer Wynne Parry on Twitter @Wynne_Parry. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.