NOAA: U.S. Had Fourth Warmest Spring; Persistent Or Worsening Drought Conditions In Many Parts Of Nation

The contiguous United States experienced its fifth warmest May and fourth warmest spring since records began in 1895, while overall precipitation remained below average, according to scientists at the National Oceanic & Atmospheric Administration's (NOAA) National Climatic Data Center in Asheville, N.C. Also, the June 2005 to May 2006 period was the warmest on record for the contiguous United States, NOAA announced on June 19.

The continuation of below-normal precipitation combined with much warmer than average temperatures led to persistent, or in some cases worsening, drought conditions in many parts of the nation. Meanwhile, portions of New England experienced flooding in May as a series of storms set many local rainfall records. The global surface temperature was the fifth warmest on record for May.

U.S. Temperatures

The average temperature for the contiguous United States for May (based on preliminary data) was 63.7 degrees Fahrenheit or 2.7 degrees Fahrenheit above the 20th century (1901 to 2000) average. The March to May period was the fourth warmest spring for the contiguous United States, and four states (Arkansas, Oklahoma, Kansas and Texas) experienced their warmest spring on record. No state had below-average spring temperatures, and only California was near average. This continued the string of warmer-than-average conditions over the past year in the contiguous United States.

U.S. Precipitation

May 2006 precipitation across the contiguous United States was below average, at 2.33 inches -- 0.54 inches below the 20th century average. Most of the central United States was drier than normal, but only Nebraska and Iowa were much drier than average. A series of storms in the northeastern United States resulted in well-above normal rainfall totals from Michigan and Indiana across to New England. New Hampshire and Massachusetts both experienced their second wettest May on record. This is largely due to the exceptional rainfall event of May 10 to 15, when accumulations of between 12 and 17 inches (300 to 430 mm) of rain occurred in some localities.

Spring 2006 also was drier than average for the contiguous United States, with the most anomalously dry conditions along the eastern seaboard from New Jersey to Florida. Areas from the Gulf Coast to Wyoming also were drier than average. Parts of the Far West, northern Rockies and Midwest, along with Vermont and New Hampshire were wetter than average.

Persistent drier-than-average conditions over the past several months, combined with much above average to record warmth, worsened drought conditions. By early June, moderate-to-severe drought was present throughout a large part of the south-central United States, with extreme and exceptional drought occurring in the parts of the Desert Southwest, southern Plains and southeastern Louisiana, according to the U.S. Drought Monitor. Moderate drought developed in central Florida and grew to encompass parts of the southern Appalachian region. Fully 39 percent of the contiguous United States was in moderate-to-extreme drought, while 20 percent was in severe-to-extreme drought, as defined by the Palmer Drought Index, a widely used measure of drought. Above average precipitation alleviated moderate drought conditions in the Upper Peninsula of Michigan, and conditions improved in areas that included eastern Oklahoma, southern Florida and parts of the Northeast.

NOAA National Climatic Data Center:

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