Drought and Hail Create Havoc During September

September's weather story was dominated by two of Oklahoma’s most damaging hazards—severe drought and a devastating hailstorm. Drought had been spreading and intensifying in the state since early summer according to the U.S. Drought Monitor, and increased even further during September from 48% at the end of August to 57% by the end of the month. The area considered to be in more intense drought nearly doubled, from 18% to 33% over the same period. The worst-hit areas stretched from southwest Oklahoma to the northeast, reaching into far northeastern parts of the state. Drought was also spreading and intensifying east along the Red River toward the Arkansas border. The Oklahoma Climatological Survey received numerous reports from agricultural producers of dry farm ponds, dead or dormant grass, and withered crops. The hailstorm dropped golf ball- to nearly baseball-sized hail from northwest of Oklahoma City, through Edmond, to southeast of Norman. The hailstones—at times driven by winds exceeding 60 mph—destroyed roofs and shattered windows in homes, businesses, and automobiles.

Rain was scarce across most of the state during September. According to preliminary data from the Oklahoma Mesonet, the statewide average rainfall total was 1.49 inches—1.83 inches below normal—ranking as the 20th-driest September since records began in 1895. The northeast corner of the state was particularly dry, with an average of 0.61 inches, making it the fifth-driest September on record for that region, with a deficit of 3.35 inches. Deficits of 2 to 4 inches were common across much of the southeastern two-thirds of Oklahoma, while surpluses of about an inch were typical in the far northwest and the Panhandle. Rainfall totals ranged from 5.5 inches at Idabel to 0.11 inches at Copan. Fifty-one of the Mesonet’s 120 sites recorded less than an inch for the month, and 16 of those sites reported a half-inch or less. The first nine months of the year ended as the 61st-driest on record, with 26.14 inches of rain—2.43 inches below normal.

The statewide average temperature for September was 74.5 degrees, 1.6 degrees above normal, ranking as the 42nd-warmest on record. That ranking was bolstered by a mid-month heat wave, which saw temperatures soar into the triple digits after a brief respite during the first 10 days of the month. Temperatures ranged from 107 degrees at Freedom on Sept. 20 to 41 degrees at several stations on Sept. 9, 10, and again on the 23rd. Summer-like humidity made an unfortunate return during the mid-month hot spell, driving the heat index as high as 110 degrees at Foraker on the 19th. There were 154 instances of heat index values reaching at least 105 degrees during September, and another 229 readings of at least 100 degrees. The warmer-than-normal month added to an already hot year; the first nine months of 2023 ranked as the fifth-warmest statewide, with an average temperature of 65.7 degrees—2 degrees above normal.

The Climate Prediction Center's outlook for October is bleak, with greatly increased odds of below-normal precipitation across the entire state and increased odds of above-normal temperatures, especially in the western half. With those two key drought ingredients in the forecast, the CPC's drought outlook calls for the hazard to spread across most of the southeastern three-fourths of Oklahoma, while persisting and possibly intensifying in areas where drought already exists. To compound the dismal forecast, La Niña is given at least a 70% chance of developing during the October-November period and persisting through the winter. This cooling of the waters in the equatorial Pacific off the coast of South America, along with its associated changes in atmospheric circulation, shifts the odds toward warmer and drier conditions across the Southern Tier of the United States, including Oklahoma.