“Persistent, scorching heat” in the eastern and central United States made last month the fourth warmest July on record nationally and exacerbated drought conditions in the South, according to scientists at the National Oceanic and Atmospheric Administration’s (NOAA) National Climatic Data Center.

The average U.S. temperature in July was 77 degrees Fahrenheit, which was 2.7 degrees above the long-term 1901-2000 average, NOAA said. Oklahoma and Texas had their warmest months ever on record, with average temperatures of 88.9 and 87.1 degrees, respectively, and Oklahoma’s statewide average temperature was the warmest monthly temperature on record for any state during any month.

The South climate region — Arkansas, Kansas, Louisiana, Mississippi, Oklahoma, and Texas — had its warmest single calendar month for any climate region on record, and 41 of the Lower 48 states had above-normal, much-above-normal or a record warmest July, NOAA said.

NOAA has said that the El Nino-Southern Oscillation and the Arctic Oscillation affected regional climates and contributed to many of the world’s significant weather events in 2010, including global temperatures that were among the warmest on record (see Daily GPI, June 29). Three major independent data sets showed 2010 as one of the two warmest years since official record keeping began in the late 19th century, according to NOAA.

Much of the country will have to put up with warmer-than-normal temperatures for some time, according to at least one forecaster. Summer heat, which has so far been “more impressive and widespread than anticipated,” will continue to blanket most of the country in August and into the autumn, according to Andover, MA-based WSI Corp. (see Daily GPI, July 26).

But WSI’s steamy outlook is significantly different than MDA EarthSat Weather’s forecast of summer temperatures averaging 14.5% cooler than last year (see Daily GPI, May 18), while AccuWeather.com forecasters have said they expect the lingering effects of a recent La Nina event to translate into a “year without a summer” for the nation’s midsection (see Daily GPI, June 1).

Precipitation, which averaged 2.46 inches across the nation in July, was 0.32 inch below the long-term average, with large variability between regions, according to NOAA. The heat resulted in the largest “exceptional” drought footprint — the most severe category of drought on the drought monitor scale — in the 12-year history of the U.S. Drought Monitor. Drought conditions at several locations in the South region are as dry or drier than the historic droughts of the 1930s and 1950s, but are not as long-lived, NOAA said.

More than 75% (201,436 square miles) of Texas is experiencing exceptional drought, with some locations needing as much as 20 inches of precipitation in one month to end the drought. In Oklahoma, 100% of the state is suffering from moderate-exceptional drought. Conversely, wetter-than-normal conditions occurred in July along parts of the Gulf Coast, all of the Pacific Coast and much of the upper Midwest.

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