NOAA: U.S. Experienced Its Second-Hottest July On Record; Drought Conditions Worsening

Coming as no surprise to U.S. residents sweating out the summer, the National Oceanic & Atmospheric Administration (NOAA) stated on Aug. 7 that the continental United States suffered through its second-hottest July on record because of a blistering heat wave from California to Washington, D.C.

The heat wave broke more than 2,300 daily temperature records for the month and eclipsed more than 50 records for the highest temperatures in any July, according to the NOAA National Climatic Data Center in Asheville, N.C. The hottest July on record occurred in 1936, and the third hottest was 1934.

The agency also reported that the first seven months of 2006 was the warmest January-July of any year the United States since records began in 1895. And, the scorching temperatures, combined with a shortage of rainfall, expanded moderate-to-extreme drought conditions in areas already hard hit.

U.S. Temperature

The average July 2006 temperature for the contiguous United States (based on preliminary data) was 77.2 degrees Fahrenheit (25.1 Celsius). More than 90 records for the highest night-time temperatures for July were broken. The average January to July 2006 temperature was 55.3 degrees Fahrenheit (12.9 Celsius), which beat the previous record set in 1934.

The Residential Energy Demand Temperature Index (REDTI), which provides information related to climate sensitive residential energy demand, ranked as the fourth highest July index in the 112-year record. Using this index, NOAA scientists determined that the nation's residential energy demand was approximately 22 percent higher than that which would have occurred under average climate conditions for the month.

The average July temperature (based on the statistical mean from 1901 - 2000) is 74.3 degrees Fahrenheit. The July 1936 record temperature was 77.5 degrees Fahrenheit. The July 1934 average temperature (third highest on record) was 77.1 degrees Fahrenheit. The previous January to July cumulative record temperature was 54.8 degrees Fahrenheit (set in 1934).

NOAA scientists add that no single episode of extreme heat can be blamed exclusively on human-induced global warming, but instead heat waves will become more likely and progressively more intense over the course of decades. Changes in the frequency and intensity of heat waves across North America will be comprehensively assessed in the forthcoming Climate Change Synthesis and Assessment Product 3.3.

U.S. Precipitation

The average precipitation for July 2006 across the continental United States was 0.18 inch (4.6 mm) below the 20th century average, contributing to a January to July period that was 22nd driest on record.

In July, 51 percent of the United States, mostly in the Plains states and Southeast, was in moderate-to-extreme drought (based on the Palmer Drought Index), an increase of five percent from June. This percentage ranks with the biggest droughts of the last 50 years. The most extensive drought occurred in July 1934 when 80 percent of the country was affected by moderate-to-extreme drought. In addition, 28 percent of the country, mainly in the Plains states, was in severe-to-extreme drought in July, up from 27 percent in June.

For additional information, see "NOAA National Climate Summary: July 2006" at http://www.ncdc.noaa.gov/oa/climate/research/2006/jul/currentmonth.html.

This article originally appeared in the 08/01/2006 issue of Environmental Protection.

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