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Wednesday, April 11, 2012

Jeff Masters: March 2012 -- Warmest in U.S. History

March 2012 -- Warmest in U.S. History

by Jeff Masters, Ph.D., WunderBlog, April 10, 2012

Not only was March 2012 the warmest March in the U.S. since record keeping began in 1895, it was also the second most extreme month for warmth in U.S. history, said NOAA yesterday, in their monthly "State of the Climate" report. The average temperature of 51.1 °F was 8.6 degrees above the 20th century average for March, and 0.5 °F warmer than the previous warmest March in 1910. Of the more than 1,400 months that have passed since the U.S. weather records began in 1895, only one month -- January 2006 -- had a larger departure from its average temperature than March 2012. A remarkable 25 states east of the Rockies had their warmest March on record, and an additional 15 states had a top-ten warmest March. Only four states were cooler than average, with Alaska being the coldest (tenth coldest March on record.)

Figure 1. Temperature rankings for March 2012 in the Contiguous U.S. Twenty-five states set records for warmest March in the 118-year records (red colors.) Image credit: NOAA.

March 2012: most daily records broken of any month since July 1936
A wunderground analysis of weather records from NOAA's National Climatic Data Center temperature record database reveals that more daily high temperature records were broken in March in 2012 than for any month except July 1936, going back at least 100 years. Fully 11.3% of all daily high temperature records for the month of March in the U.S. are now held by the year 2012, for the 550 stations in NOAA's National Climatic Data Center database that have weather records extending back at least 100 years. The only month in U.S. history holding a higher percentage of daily temperatures records is July 1936. That month holds 14.4% of all the U.S. high temperature records for the month of July. That month occurred in the great Dust Bowl summer of 1936, the hottest summer in U.S. history.

Summer in March 2012: records not merely smashed, but obliterated
Among the 15,000 daily records for warmth set in March 2012 were 21 truly astonishing ones: cases where the low temperature for the day beat the previous high temperature for the day. It is quite rare for a weather station with a 50+ year period of record to break a daily temperature record by more than 10 °F. During "Summer in March 2012," beating daily records by 10-20 °F was commonplace, and NOAA lists 44 cases where a daily record was broken by more than 22 °F. Extraordinarily, four stations broke a record for the date by 30 °F or more. Canada holds the most surreal record of this nature during the "Summer in March 2012" heat wave: Western Head, Nova Scotia, hit 29.2 °C (85 °F) on March 22, breaking their previous record for the date (10.6 °C in 1969) by 18.6 °C (33.5 °F). Canada also had several stations break their all-time warmest April temperature records in March.

Last 3 months and 12 months were the warmest on record
The previous 12-month period (April 2011-March 2012), which includes the second hottest summer (June-August) and fourth warmest winter (December-February), was the warmest such period for the contiguous United States. The year-to-date period (January-March) was also the warmest on record. NOAA's U.S. Climate Extremes Index, an index that tracks the highest 10% and lowest 10% of extremes in temperature, precipitation, and drought, was 39%, nearly twice the long-term average and the highest value on record for the January-March period. The predominant factor was the large area experiencing extremes in warm daily maximum and minimum temperatures.

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