July 2012 marked hottest month on record for contiguous U.S.; Drought expands to cover nearly 63 percent of the Lower 48

During July, the contiguous U.S. averaged a precipitation total of 2.57 inches, which was 0.19 inch below average. Near-record dry conditions were present for the middle of the nation, with the drought footprint expanding to cover nearly 63 percent of the Lower 48, according the U.S. Drought Monitor, while some areas such as the Gulf Coast and the Southwest had wetter-than-average conditions.

This monthly analysis (summary, full report) from NOAA's National Climatic Data Center is part of the suite of climate services NOAA provides government, business and community leaders so they can make informed decisions.

U.S. climate highlights -- July

• Higher-than-average temperatures engulfed much of the contiguous U.S. during July, with the largest temperature departures from the 20th century average occurring across most of the Plains, the Midwest, and along the Eastern Seaboard. Virginia had its warmest July on record, with a statewide temperature 4.0°F above average. In total, 32 states had July temperatures among its ten warmest, with seven states having their second warmest July on record.
• Drier-than-average conditions continued across the Central Plains and Midwest during July. Nebraska, Iowa, Illinois, and Missouri had July precipitation totals ranking among their ten driest. Maine had its fifth driest July on record.
• An active storm pattern in the Southwest contributed to California having its fifth wettest July on record and Nevada having its eighth wettest. Wetter-than-average conditions were also observed through the rest of the Southwest, along the western Gulf Coast, and through the Ohio Valley where West Virginia had its tenth wettest July.
• The warm and dry conditions over a large portion of the country were associated with ideal wildfire conditions. Over 2 million acres were burned nationwide during July due to wildfires, nearly half a million acres above average, and the fourth most on record since 2000.

Drought conditions update

• The May-July months, an important period for agriculture, was the second warmest and 12th driest such three-months for the Lower 48, contributing to rapid expansion of drought. The central regions of the country were hardest hit by the drought, where ten states had three-month precipitation totals among their ten driest, including Nebraska, Kansas, and Arkansas which were record dry.
• According to the July 31, 2012, U.S. Drought Monitor (USDM), 62.9 percent of the contiguous U.S. was experiencing moderate to exceptional drought at the end of July. This is an increase of about 6.9 percent compared to the end of June. The maximum value of 63.9 percent reached on July 24 is a record in the 13-year history of the USDM.
• The area of the country in the worst drought categories (extreme to exceptional drought) doubled from 10 percent last month to 22 percent this month. The extreme dryness and excessive heat devastated crops and livestock from the Great Plains to Midwest.
• The Primary Corn and Soybean Agricultural Belt, hard hit by drought, experienced its eighth driest July, third driest June-July, and sixth driest April-July (growing season) in the 1895-2012 record.
• According to the Palmer Drought Severity Index, whose record spans the 20th century, about 57 percent of the contiguous U.S. was experiencing moderate-to-extreme drought in July. The last drought this extensive was in December 1956 when about 58 percent of the nation was in moderate-to-extreme drought.

Year-to-date (January-July)

• The January-July period was the warmest first seven months of any year on record for the contiguous United States. The national temperature of 56.4°F was 4.3°F above the long-term average. Most of the contiguous U.S. was record and near-record warm for the seven-month period, except the Pacific Northwest, which was near average.
• The first seven months of 2012 were drier than average, ranking as 15th driest January-July on record. Below-average precipitation totals were observed for a large portion of the country, with 12 states having January-July precipitation totals among their ten driest. Above-average precipitation was observed for the Upper Midwest and the Pacific Northwest.
• The U.S. Climate Extremes Index (USCEI), an index that tracks the highest and lowest 10 percent of extremes in temperature, precipitation, drought and tropical cyclones across the contiguous U.S., was a record-large 46 percent during the January-July period, over twice the average value, and surpassing the previous record large CEI of 42 percent which occurred in 1934. Extremes in warm daytime temperatures (83 percent) and warm nighttime temperatures (74 percent) both covered record large areas of the nation, contributing to the record high year-to-date USCEI value.

12-month period (August 2011-July 2012)

• The August 2011-July 2012 period was the warmest 12-month period of any 12-months on record for the contiguous U.S., narrowly surpassing the record broken last month for the July 2011-June 2012 period by 0.07°F. The nationally averaged temperature of 56.1°F was 3.3°F above the long term average. Except Washington, which was near average, every state across the contiguous U.S. had warmer than average temperatures for the period.

Additional information can be found on the following web sites:

• NOAA July U.S. Climate Report: http://www.ncdc.noaa.gov/sotc/national/2012/7
• NOAA Climate Portal: http://www.climate.gov/
• U.S. Drought Monitor: http://www.drought.gov/