State of the Climate National Overview May 2012

• Climate Highlights — spring (March-May)
• The national temperature of 57.1 degrees F during spring was 5.2 degrees F above the long-term average, besting the previous warmest spring of 1910 by 2.0 degrees F. This marked the largest temperature departure from average of any season on record for the contiguous United States. The spring of 2012 was the culmination of the warmest March, third warmest April, and second warmest May. This marks the first time that all three months during the spring season ranked among the ten warmest, since records began in 1895.
• Record and near-record warmth dominated the eastern two-thirds of the nation during spring. Thirty-one states were record warm for the season, and 11 additional states had spring temperatures ranking among their ten warmest. Only Oregon and Washington had spring temperatures near their average.
• Spring was drier than average for the contiguous U.S. as a whole, with a national precipitation total of 7.47 inches, 0.24 inch below average.
• Wetter-than-average conditions prevailed from the West Coast through the Northern Plains and into the Upper Midwest. Oregon was record wet and Minnesota and Washington were third wettest, compared to their spring histories. The Intermountain West, Ohio Valley, and parts of the Mid-Atlantic were drier than average. Colorado, Utah, Wyoming, Indiana, and Delaware had a top ten dry spring.
• 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 44 percent during the March-May period, over twice the average value. Extremes in warm daytime temperatures (81 percent) and warm nighttime temperatures (72 percent) covered large areas of the nation, contributing to the record high value.
• The warmer-than-average conditions, which persisted through winter and spring, limited snowfall over a large portion of the country. According to the Rutgers Global Snow Lab, the spring snow cover extent across the contiguous U.S. was the third smallest on record.
• A list of select May and spring temperature and precipitation records can be found here.
• Climate Highlights — May
• The average temperature for the contiguous U.S. during May was 64.3 degrees F, which is 3.3 degrees F above average — the second warmest May on record
• Warmer-than-average temperatures were present for all regions except the Northwest, with the largest departures from average across the Central Plains, Midwest, and Northeast. Twenty-six states had May temperatures ranking among their ten warmest.
• Precipitation patterns across the contiguous U.S. were mixed during May. The Eastern Seaboard and Upper Midwest were wetter than average. North Carolina, South Carolina, Vermont, New Hampshire, and Minnesota had May precipitation totals among their ten wettest. Dry conditions prevailed for the Mid-South, parts of the Southern Plains, and the Great Basin. Arkansas, Missouri, Kansas, Nevada, and Utah had a top ten dry May.
• Tropical Storm Beryl made landfall near Jacksonville, Florida on May 28^th, bringing beneficial rainfall to parts of the drought-stricken Southeast. Beryl occurred on the heels of Tropical Storm Alberto, marking only the third time on record that two tropical cyclones reached tropical storm strength during May in the North Atlantic basin.
• Ongoing drought, combined with windy conditions, created ideal wildfire conditions across the Southwest. The Whitewater-Baldy Fire complex in the Gila National Forest of western New Mexico grew out of control and charred over 210,000 acres by the beginning of June. The fire surpassed 2011’s Las Conchas Fire as the largest wildfire on record for the state.
• According to the U.S. Drought Monitor, as of May 29^th, 37.4 percent of the contiguous U.S. was experiencing drought conditions, a slight decrease from 38.2 percent at the beginning of May. Drought conditions improved across the coastal Southeast, the Southern Plains, Northeast, and Upper Midwest, while they deteriorated for parts of the Mid-South and Southwest.
• A list of select May and spring temperature and precipitation records can be found here.
• Climate Highlights — Year-to-Date (January-May)
• January-May was the warmest such period on record for the contiguous United States, with an average temperature of 49.2 degrees F, 5.0 degrees F above the long-term average. Twenty-nine states, all east of the Rockies, were record warm for the five-month period and an additional 14 states had temperatures for the period among their ten warmest.
• The year’s first five months brought dry conditions to much of the East. The Southwest to the Central Rockies was also drier than average. Wetter-than-average conditions persisted for the Pacific Northwest, Upper Midwest, and the western Gulf Coast. The national precipitation total for the five-month period was nearly 1.0 inch below average.
• For the year-to-date period, the USCEI was a record 43 percent, over twice the long-term average. As with the spring USCEI, the drivers were extremes in warm daytime temperatures (83 percent) and warm nighttime temperatures (70 percent).
• Alaskan temperatures were cooler than average for much of the first five months of 2012. The state had its 15^th coolest January-May period on record, with temperatures 3.2 degrees F below average.
• Climate Highlights — 12-month period (June 2011-May 2012)
• The June 2011-May 2012 period was the warmest 12-month period of any 12 months on record for the contiguous United States. The nationally-averaged temperature of 56.0 degrees F was 3.2 degrees F above the long-term average, surpassing the previous record, set last month (May 2011-April 2012), by 0.4 degrees F. The 12-month period encapsulated the second warmest summer, fourth warmest winter, and the warmest spring on record. Every state across the contiguous U.S. had warmer than average temperatures for the period, except Washington, which was near normal.
• Every state from the Rockies eastward had a top five warmest June-through-May period, and twenty-six states had their warmest such period on record.