May’s weather was rather tame by Oklahoma standards, with severe weather greatly diminished by an abundance of cool, cloudy weather. Plenty of moisture was to be had, with heavy rains falling right through May’s final day. That is not to say severe weather was completely absent, but at times flood warnings were seemingly more prevalent than severe thunderstorm warnings. Only a handful of tornadoes were reported in the state during May. While the official number is still under investigation by the National Weather Service, the total will come in well below the month’s 1950-2020 average of 24.3 twisters. Those that did touch down were damaging, nonetheless. An EF-1 tornado struck near Roland on May 3, destroying several outbuildings and damaging homes in the area. Another EF-1 twister damaged structures near Hanna on the 27th before dissipating. The month ended on a more violent note as at least two large tornadoes were reported in Cimarron County on the 29th. The twisters traveled over open ground mostly, threatening Boise City before dissipating. More tornadoes were reported in Cimarron County the following night as well.
Most of the state saw a surplus of moisture during the month, although a few areas did suffer from continued dry weather. The statewide average precipitation total of 5.82 inches was 0.91 inches above normal and ranked as the 37th wettest May in Oklahoma since records began in 1895. Totals of 5-10 inches were common across much of central through eastern Oklahoma, and again through the Panhandle. Some areas of north central and southwestern Oklahoma saw only 2-4 inches for the month, however, to fall on the deficit side of the ledger. The Mesonet site at Broken Bow led the state with 12.62 inches. Seventy-seven of the Mesonet’s 120 sites saw at least 5 inches of rain, with 51 of those locations receiving at least 6 inches. Newkirk brought up the rear with 2.02 inches, one of only four sites with less than 3 inches for the month. May brought the climatological spring (March-May) to a close as the 30th wettest on record statewide with an average of 12.44 inches, 1.32 inches above normal. The first 5 months of the year continued on the wet side at 15.48 inches, the 37th wettest January-May on record and 0.97 inches above normal.
The statewide average temperature was 65.6 degrees according to preliminary data from the Oklahoma Mesonet, 2.7 degrees below normal and ranked as the 15th coolest May since 1895. The cooler weather was mainly a result of diminished high temperatures throughout the month, as opposed to lower minimum temperatures. Statewide average high temperatures were below their long-term averages as many as 24 days in May. Only 58 readings of at least 90 degrees were observed by the 120 Mesonet sites during the month, on just five separate days. Hollis recorded the month’s highest temperature with 97 degrees on May 8. Nowata reported the lowest temperature of 35 degrees on May 5, marking April 24 in the Panhandle as Oklahoma’s final spring freeze. Spring finished at 59 degrees, 0.3 degrees below normal to rank as the 63rd coolest March-May on record. The year remained on the cold side at 49.9 degrees, 1.8 degrees below normal and the 32nd coolest January-May on record.
Drought coverage in Oklahoma was reduced by over half during May, from 20 percent of the state at the end of April to less than 8 percent to end May. Only two small pockets of moderate-to-severe drought were left in southwestern and south central Oklahoma. The Climate Prediction Center’s (CPC) June outlooks gave promise to a possible drought free Oklahoma by the end of June. The outlooks show increased odds for above normal rainfall and below normal temperatures across virtually the entire state. Given those expectations, CPC’s June drought outlook calls for improvement or removal of the remaining areas of drought in Oklahoma.