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NOAA: Spring cooler and wetter

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May Extreme Weather/Climate Events

Supplemental May 2013 Information


  • Climate Highlights — May
  • The May average temperature for the contiguous U.S. was 61.0°F, which was 0.9°F above the 209th century average. May ranked as the 409th warmest such month on record.
  • The southeastern U.S. was cooler than average, while the rest of the nation had near and above-average May temperaturesFlorida had its 119th coolest May, and Georgia had its 129th coolest, with monthly temperatures 1.5°F and 2.6°F below average, respectively.
  • May precipitation, averaged across the contiguous U.S., was 3.34 inches, 0.47 inches above average, and the179th wettest May on record. It was also the wettest May since 1995.
  • Most of the northern U.S. had above-average May precipitationIowa had its wettest May on record with 8.84 inches of precipitation, 4.77 inches above average. Montana and North Dakota each had one of their top ten wettest Mays. The above-average precipitation contributed to flooding along several major rivers in the region including the Mississippi River and the Illinois River.
  • According to the June 4 U.S. Drought Monitor Report, 44.1 percent of the contiguous U.S. was experiencing moderate-to-exceptional drought, smaller than the 46.9 percent at the beginning of May. Drought continued to improve for parts of the Great Plains, but worsened in the West. Several months of warm and dry conditions in California led to nearly the entire state being in drought by early June.
  • Despite a below-average preliminary tornado count during May for the contiguous U.S., several large and powerful tornadoes hit populated areas resulting in significant damage and loss of life. Two EF-5 tornadoes, the highest strength rating given to a tornado, were confirmed near Oklahoma City. The EF-5 tornado that hit Moore, Oklahoma, on May 209th destroyed thousands of homes and businesses in and around the city and was blamed for over 20 fatalities. According to preliminary analysis, the EF-5 near El Reno, Oklahoma, on May 31St had a path width of approximately 2.6 miles, the widest tornado ever observed in the United States. These two events were only the 79th and 89th EF-5 tornadoes confirmed in Oklahoma in the 64-year period of record.
  • Several late-season winter storms impacted the U.S. during May, bringing snowfall to the Central and Northern Plains, as well as the Northeast, while below-average snow cover continued for the West. According to data from the Rutgers Global Snow Lab, the May snow cover extent of 6,564 square miles was 56,757 square miles below the 1981-2010 average, and the second smallest May snow cover extent on record.
  • Based on NOAA's Residential Energy Demand Temperature Index (REDTI), the contiguous U.S. temperature-related energy demand ranked as the 79th lowest May value in the 119-year period of record.
  • Climate Highlights — spring (March — May)
  • The spring average temperature for the contiguous U.S. was 50.5°F, 0.5°F below the 209th century average, making it the 389th coolest spring on record and the coolest spring since 1996.
  • Spring 2013 marked the first season in the contiguous U.S. that the seasonal temperature was not above average since the winter of 2010-2011, when the seasonal temperature was 0.8°F below average.
  • Spring was cooler than average for a large portion of the contiguous United States, east of the Rockiest.Fourteen states, from North Dakota to Georgia, had spring temperatures that ranked among the ten coldest.
  • New England and the West were both warmer than average. California had its seventh warmest spring on record with a seasonal temperature 3.5°F above average.
  • The spring precipitation total for the nation of 7.92 inches was 0.21 inch above average. The nationally-average precipitation total masked regional wet and dry extremes during the season.
  • Iowa had its wettest spring on record with 17.61 inches of precipitation, 8.63 inches above the seasonal average. Wetter-than-average conditions were observed in the Northern Plains and Midwest, where North DakotaMinnesotaWisconsinIllinois, and Michigan each had one of their top ten wettest spring seasons.
  • Below-average precipitation was observed in the Mid-Atlantic, Southern Plains, and West. New Mexico had its second driest spring with 0.66 inches of precipitation, 1.72 inches below average. California had its eighth driest spring, with 2.34 inches of precipitation, 3.33 inches below average.
  • The above-average precipitation and below-average temperatures in the north-central United States were associated with a spring snow cover extent that was above average. According to data from the Rutgers Global Snow Lab, the spring snow cover extent was the eighth largest on record and the largest since 1984.
  • The U.S. Climate Extremes Index (USCEI), an index that tracks the highest and lowest 10 percent of extremes in temperature, precipitation and drought across the contiguous U.S., was 140 percent of averageduring spring. The above-average USCEI was driven by extremes in below-average temperatures, extremes in 1-day precipitation totals, and the spatial extent of drought.
  • Climate Highlights — year-to-date (January — May)
  • The year-to-date national temperature of 43.6°F was 0.2°F above the 209th century average. Below-average temperatures were observed for much of the central United States, from Rockiest to the Mid-Atlantic. TheNortheast and parts of the West had above-average year-to-date temperatures.
  • The January-May precipitation total for the contiguous U.S. was 12.28 inches, 0.33 inch above average. North DakotaMinnesotaWisconsinMissouri, and Mississippi each had a top ten wet 5-month period; IowaIllinois, and Michigan were record wet during January-May.
  • The West, Southern Plains, and Northeast were drier than averageOregonNevadaIdaho each had a top ten dry year-to-date period, while California had its driest January-May on record with 4.09 inches of precipitation, 9.87 inches below average.
  • During both the year-to-date and 3-month timescales, the number of fires, acreage burned, and acres burned per fire were record low.
  • The USCEI for the year-to-date period was near average. However, several of the components were above average. The component for extremes in 1-day precipitation totals was 200 percent of average and the highest value on record for the 5-month period, while the component that examines the spatial extent of drought was 270 percent of average and the ninth highest