In defiance of spring, Mother Nature slipped right into summer during May, and broke a major record in doing so. Based on preliminary data from the Oklahoma Mesonet, the month finished as the warmest on record with a statewide average of 74.6 degrees, 6.4 degrees above normal. The previous record of 74 degrees was set back in 1962. This abrupt transition was especially jarring coming directly after the second coolest April on record. The heat was unkind to those battling severe drought conditions, but sporadic heavy rains did lend improvements to some. The statewide average precipitation total of 3.99 inches fell 0.83 inches below normal to rank as the 48th driest May on record.
As Mays go in Oklahoma, this year’s chapter was relatively quiet, but severe weather did make itself known at times. Oklahoma’s longest streak without a tornado to begin a year ended on May 2 with at least 15 tornado touchdowns. The Hollis Mesonet site recorded a wind gust of 81 mph on the 14th, damaging trees and outbuildings. Baseball size hail propelled by winds up to 79 mph produced significant damage around Erick in Beckham County on the 29th.
May’s high temperatures rarely reached the extreme category with only a few triple-digit readings during the month’s final week. Temperatures consistently rose into the 90s, however, and heat index values thrived in the high-moisture environment common during May, topping out at 113 degrees at Grandfield on the 31st. That site recorded the month’s highest temperature of 104 degrees that same day. The lowest temperature of 37 degrees was reported by the Eva Mesonet site on May 5. May also marks the end of climatological spring. Combined with a warm March and chilly April, the record-setting May propelled the season to the 30th warmest spring on record with a statewide average of 60.5 degrees, 1.2 degrees above normal. The first five months of the year came in 0.3 degrees above normal to rank as the 41st warmest January-May on record.
Rain totals were highly variable across the state, befitting the convective nature of spring rains in Oklahoma. Parts of southeastern Oklahoma fell close to 5 inches below normal, while isolated areas in northwestern Oklahoma were more than 5 inches above. The Mesonet site at Alva in Woods County recorded 9.2 inches for the month while the Fairview site 40 miles away received 1.5 inches. Those tight gradients were evident throughout Oklahoma. The 9.2 inches at Alva led the state, while Kenton brought up the rear with 0.9 inches. Drought was threatening to develop once again across eastern Oklahoma in those areas with significant deficits. Climatological spring ended as the 22nd driest on record with a statewide average of 8 inches, 3.12 inches below normal. The January-May period was the 49th driest with a statewide average deficit of 1.9 inches.
Drought decreased across the state by a mere 2 percent during May according to the U.S. Drought Monitor, but “Exceptional” drought – the Monitor’s highest intensity level – dropped from 24 percent to 10 percent. A little over 45 percent of the state remained in some level of drought by the end of the month. The Climate Prediction Center (CPC) had little good to say in their June outlooks. Their temperature outlook had greatly increased odds of above normal temperatures across the entire state, but especially the western half. The precipitation outlook indicated increased odds of below normal precipitation for Oklahoma, with higher odds across the western two-thirds. Those outlooks led to a CPC June drought outlook that called for drought to persist across the northwestern half of the state with development likely across the southeastern half.