The Winter That Wasn’t Checks In at Fourth Warmest

The stats are in on the winter that wasn’t, and the December through February period stacks up as the fourth-warmest winter on record for the Lower 48 states, according to newly released numbers from the National Oceanic and Atmospheric Administration (NOAA).

The average temperature for the Lower 48 states during the December through February period, the time span defined as meteorological winter, was 3.9 degrees Fahrenheit above the 1901-2000 long-term average, making it the warmest winter since 2000. The other winters that were warmer than this one occurred in 1992 and 1999.

State by state temperature rankings for December through February 2011-12. Credit: NOAA/NCDC.

Winter was dominated by a northern storm track, which allowed mild air to repeatedly work its way northward, giving 27 states one of their top 10 warmest winters on record. Only one state — New Mexico — had winter temperatures below its 20th Century average, NOAA reported. In Massachusetts, February 2012 tied with February 1998 as the warmest such month on record, with average temperatures nearly 8 degrees F above average. New York's Central Park had its warmest February on record, with an average temperature of 40.9 degrees F, well above the typical monthly average of 35.3 degrees.

Interestingly, Alaska wound up having a near average seasonal temperature, despite the extreme cold that gripped the state during January.

According to the Rutgers University Global Snow Lab, wintertime snow cover extent in the Lower 48 states was the third smallest in the 46-year satellite record. The only winter seasons that had smaller snow cover extents were the winters of 1991-92 and 1980-81, NOAA reported.

Syracuse, N.Y., finished the winter season with just 42.7 inches of snowfall, which was nearly 50 inches below average. Buffalo, N.Y., was about 36 inches below average, and a similar snow drought affected much of the Northeast and other parts of the country.

It wasn’t just snow that failed to materialize. Rainfall was below average as well, particularly in the West, where California had its second-driest winter on record.

The warm weather led to a skewed relationship between warm temperature records and cold temperature records across the country. NOAA reported that there were more than 800 daily high temperature records and more than 1,200 record warm daily low temperature records set during February 2012. This compares to just 200 or so daily record cold temperatures, and about the same number of record cold daily high temperatures.

U.S. temperature trends for the months of December through February during the period 1896 through 2012, showing an overall warming trend. Click on the image for a larger version. Credit: NOAA/NCDC.

In the Midwest, cities that usually have many days with below zero low temperatures, instead saw the thermometer struggle to fall below the single digits. Minneapolis had only two days with low temperatures below zero, a far cry from the norm of 30 days. Chicago did not have a day with temperatures below zero, in fact, the coldest it got there was 5°F, nearly setting a new record for the warmest wintertime low temperature. The coldest temperature in all of Illinois this winter was -6°F, recorded in the northwestern part of the state, according to the Illinois State Climatologist.

The U.S. Climate Extremes Index, which measures the highest 10 percent and lowest 10 percent in terms of precipitation, temperature, drought and tropical cyclones, finished the season at its ninth-highest value. This means that much of the country — about one-third, to be exact — experienced climate extremes defined by the index, with much of it driven by record warm temperatures.

The warmer than average temperatures were related to a pattern of weather variability known as the Arctic Oscillation. When the Arctic Oscillation is in a “positive phase,” as it was throughout most of the winter, warmer weather is favored across much of the eastern U.S.

This does not tell the entire story, however, since long-term wintertime warming trends are taking place in part due to increasing amounts of manmade greenhouse gases in the air.