May gets top billing as Oklahoma’s rowdiest weather month, and it certainly lived up to that notoriety this year. At least three major severe weather outbreaks occurred during May. These short but intense periods of disturbed weather brought the state tornadoes, severe winds, hail to the size of grapefruits, and widespread flooding. Data from the National Weather Service suggest as many as 50 tornadoes touched down during the month, a number that could rise as more possible twisters are investigated. The state’s first tornado death since May 9, 2016, occurred with a large EF2 tornado that struck the Elk City area on May 16. The tornado, which reached 1000 yards wide at one point, was on the ground for 18 miles. The fatality occurred as it struck a vehicle, killing the driver who was fleeing the tornado. As many as eight businesses and 200 homes were damaged or destroyed along the twister’s path in Beckham County. The Oklahoma Mesonet site at Walters recorded a thunderstorm related wind gust of 104 mph on the 18th, the seventh highest wind gust recorded by the network since its inception in 1994. The small town then suffered a flash flood the following evening. The last severe outbreak of the month hit the state on the 27th into the 28th with damaging hail, severe winds and numerous tornado warnings.
According to preliminary data from the Oklahoma Mesonet, the statewide average precipitation total was just a tad below normal at 4.66 inches. The rainfall totals were quite variable across the state, however. Mesonet sites in the Panhandle and a broad swath from south central into the northeast ranged from 1-4 inches above normal. Interspaced in between was an even larger area of below normal totals, with deficits of 1-4 inches. The far southeast also came in 2-3 inches below normal. Tishomingo led the Mesonet with 10.05 inches while Tipton brought up the rear with an inch. May’s totals end a climatological spring season (March-May) that saw impressive surpluses erase equally impressive deficits. The spring statewide average was 13.78 inches, nearly 3 inches above normal to rank as the 19th wettest on record. The northeast and Panhandle areas experienced their fifth and sixth wettest spring on record, respectively. The totals exceeded normal by 8-10 inches across the northeast. There were small pockets of 1-4 inch deficits across southern Oklahoma. The January-May statewide average ended at 18.4 inches, 3.89 inches above normal to rank as the 14th wettest such period on record. The wet spring eradicated the last traces of drought within Oklahoma by the end of May, per the U.S. Drought Monitor. It was the first drought-free report for the state since June 21, 2016. Over 73 percent of the state was in drought at the beginning of March.
The wet, stormy weather ensured Oklahoma’s first cooler than normal month since December 2016. The statewide average temperature of 66.6 degrees fell 1.6 degrees below normal to rank as the 34th coolest May on record. While the month itself was mild, one weekend was befitting of mid-summer. Temperatures rose into the upper 90s and 100s from the 25th through the 27th. Combined with a strong flow of moisture from the Gulf of Mexico, the heat index rose even higher, prompting a heat advisory for central and southern Oklahoma. Burneyville registered a heat index of 110 degrees on the 27th. Altus and Grandfield recorded the highest actual air temperature of 102 degrees that same day. The lowest reading was 29 degrees at Kenton on May 1 – also the state’s last freeze. The first five months of the year ended at 55 degrees, the third warmest such period on record.
The outlooks for both temperature and precipitation favor a mild, wet month to come, with increased odds of below normal temperatures and above normal precipitation. Accordingly, the drought outlook for June indicates drought development is unlikely.