U.S. again marks warmest 12 months on record

For the second consecutive month, the U.S. has marked its warmest 12-month period on record.

Nationwide, the average temperature of 56 degrees from June 2011 to May 2012 was 3.2 degrees above-average. The previous record, set for the period of May 2011 to April 2012, was 0.4 degrees cooler. Three of the top-10 warmest 12-month periods on record have ended in 2012.

This is all according to a monthly "State of the Climate" report from the National Climatic Data Center.

The average for the year ending in May was particularly pushed upward by the fact that the meterological spring was the warmest on record for the country, just as it was at BWI Marshall Airport. It was also the hottest spring on record for all of Maryland and for 30 other states across the eastern two-thirds of the country.

That came after of the fourth-warmest winter and second-warmest summer on record nationwide.

Average temperatures in Baltimore for the year to date are running as much as 6 degrees above normal, as this graph from the NCDC shows. The thick red line at the top of the graph shows just how much temperatures are running high relative to the next warmest years on record.

Could June and summer 2012 snap the trend? About a week into the month, the average temperature at BWI is 3.4 degrees below normal at 65.4 degrees. AccuWeather.com predicted a summer without prolonged heat waves for the mid-Atlantic, but the National Weather Service's Climate Prediction Center is predicting good chances for a warmer-than-average summer.

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