Largely deprived of its primary rainy season, Oklahoma saw drought surge across the state during June. A mid-month bout with showers and storms managed to stem the flash drought’s intensification and spread with beneficial rains across northwestern Oklahoma. The respite was brief, however. Dry weather and intense heat returned by the end of the month and drought was again on the move to the south and east. Contained wholly within the western half of the state at the end of May, drought had progressed to the state’s eastern border by the end of June. Drought coverage leapt from 14% of the state to 43% over that same period according to the U.S. Drought Monitor. That was the highest coverage of drought Oklahoma had seen since Aug. 14, 2018. Much of the western Panhandle was covered by extreme drought, and exceptional drought bled down from Kansas and Colorado into far northern Cimarron and Texas counties. The Drought Monitor’s intensity scale slides from moderate-severe-extreme-exceptional, with exceptional being the worst classification.
Normally the wettest part of the year in Oklahoma, the mid-May through mid-June period was dominated by a large dome of high pressure over the Southern Plains that limited chances for significant moisture. The mid-month storm system managed to partially salvage the primary spring rainy season for Oklahoma, but significant deficits remained following its exit. According to preliminary data from the Oklahoma Mesonet, the statewide average rainfall total was 1.97 inches, 2.55 inches below normal and ranked as the 15th driest June since records began in 1895. Most of the state ended with deficits of 1-3 inches, with the lowest totals being reported across eastern Oklahoma. Deficits there reached 5 inches in some locations and amounted to less than 10 percent of their normal June rainfall. The Mesonet site at Walters led the reports with 6.32 inches, one of only four Mesonet stations out of 120 to receive at least 5 inches of rain. Sixty-seven sites recorded less than 2 inches for the month. Tulsa had the state's lowest total at 0.11 inches, its driest June since local records began in 1893. The January-June precipitation total of 20.1 inches was 1.07 inches above normal to rank as the 33rd wettest on record, but rainfall varied wildly from one region to the next. Deficits across the northwestern half of the state ranged from 2-6 inches while the southeastern half saw surpluses balloon to nearly 17 inches above normal.
June’s weather was scorching hot during the first half of the month, and ended much the same. Sandwiched in between was a 10-day period of pleasantly cooler than normal weather, a fringe benefit of the mid-month storm system that brought moisture to the state. Altogether, the statewide average of 78.5 degrees was 2 degrees above normal to rank as the 32nd warmest June on record. The top reading in the state was 109 degrees at Altus and Erick on June 30, and the lowest was a chilly 40 degrees from both Eva and Kenton on June 10. The mid-month moisture made for sultry conditions when the heat returned to end the month. The heat index soared as high as 113 degrees at several locations on June 30. The Mesonet’s 120 stations reported a heat index of at least 105 degrees 191 times during the month. The warm June continued a pattern for 2020. The January-June statewide average of 57.2 degrees was 1.5 degrees above normal to rank as the 16th warmest such period on record.
Drought development across the remainder of Oklahoma – save for the southeast quarter – is considered “likely” according to the Climate Prediction Center’s (CPC) drought outlook for July. The existing drought across the northwestern third of the state is expected to persist and possibly intensify. CPC’s negative stance is a result of equally unpleasant July outlooks for precipitation and temperature that indicate increased odds for above normal temperatures and below normal precipitation across Oklahoma. The odds for below normal precipitation are enhanced across much of western and central Oklahoma.