The May precipitation total for the contiguous U.S. was 4.36 inches, 1.45 inches above average. This was the wettest May on record and the all-time wettest month in 121-years of record keeping. The previous wettest May was in 1957 when 4.24 inches of precipitation was observed. The previous wettest month was October 2009 when 4.29 inches of precipitation was observed.
Wetter than average conditions were widespread across the central United States. Fifteen states from the Great Basin to Mississippi River had precipitation totals that were much above average. Colorado, Oklahoma, and Texas were each record wet for the month. In fact, Oklahoma and Texas each had their wettest month of any month on record with precipitation totals more than twice the long-term average.
The Oklahoma May precipitation total of 14.06 inches bested the previous wettest May of 1957 by 3.52 inches and the previous wettest month of October 1941 by 3.31 inches. The Texas May precipitation total of 8.93 inches bested the previous wettest May of 1914 by 2.31 inches and the previous wettest month of June 2006 by 2.27 inches.
The heavy precipitation during May essentially ended the multi-year drought that has plagued the Southern Plains since 2011. At the beginning of June, only 0.6 percent of Texas and 0.0 percent Oklahoma were in drought. This was the first time since 2010 that the drought footprint in both states has been this low. Although long-term (60+ months) precipitation deficits persist in some locations, some reservoirs have returned to above-average levels after being record and near-record low for the past several years.
The heavy rains in the central U.S. were accompanied by severe weather with over 400 preliminary tornado reports, the most since April 2011. The flooding rains and severe weather resulted in dozens of fatalities and widespread property damage.
Much of the East Coast was drier than average, despite the record high contiguous U.S. precipitation value and despite tropical storm Ana making landfall in the Carolinas early in the month. Seven states from the Southeast to New England had May precipitation totals that were much below average. No state was record dry.
According to NOAA data analyzed by the Rutgers Global Snow Lab, the May snow cover extent for the contiguous U.S. was 39,000 square miles, 25,000 square miles below the 1981-2010 average. This was the 18th smallest May snow cover extent for the contiguous U.S. and the smallest since 2012. The Alaska May snow cover extent was 161,000 square miles below average and the smallest May snow cover extent on record for the state. The entire state had below-average snow cover during the month. Looking further back at the entire snow season in Alaska, Anchorage only observed 25.1 inches of snow from September through May, the least snowy snow season record. The previous lowest seasonal snowfall for Anchorage was 30.4 inches in 1957/58 and normal is 74.5 inches.