The drought and relentless heat that plagued Oklahoma for months reached a crescendo during September before a rare guest came calling from the Pacific Ocean during the month’s final two days. Moisture from the remnants of Hurricane Polo spread across the High Plains and interacted with a large upper-level trough to help bring long-awaited, widespread rain to Oklahoma. By then, however, the damage was done.
The early taste of fall that delighted many Oklahomans at the end of August lingered through the first week of September before summer grabbed the remote control again. Gone were the autumn-like highs in the 60s and 70s, replaced by the more customary 80s and 90s. Despite that return to normalcy, Mother Nature couldn’t resist one more twist: for the first time since 2008, the Oklahoma Mesonet failed to record a single 100-degree temperature during September. The last triple-digit highs—likely the year’s final—came back on Aug. 28 at several sites in southwest Oklahoma.
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.
Flash drought continued to advance and intensify across the southwestern half of Oklahoma during September, aided by scorching hot weather and a prolonged dry spell that had stretched to more than 60 days in some areas. While there was some relief during September from the dry and hot conditions—the weather cooled considerably during the month’s second week to go along with heavy rains—summer weather returned soon thereafter for the remainder of the month.
Drought surged across Oklahoma as the driest September since 1956 took its toll on the state’s landscape. The amount of drought in the state remained largely unchanged through September at approximately 99%, but the intensity of that drought increased dramatically according to the U.S. Drought Monitor. Extreme and exceptional drought, the Drought Monitor’s two worst categories, jumped from 47% on Aug. 30 to 64% at the end of September, the highest such levels seen in the state since Feb. 19, 2013. Exceptional drought alone rose to 17%, its highest level since May 8, 2018.
The 17th warmest and driest September in Oklahoma since records began in 1895 allowed drought to flourish during the month. Categorized as “flash drought,” its rapid onset and intensification occur when abnormally high temperatures and below normal precipitation persist for an extended period. Most often a warm season phenomenon, abundant sunshine and strong winds can also aid in its progression. Those are precisely the conditions Oklahoma experienced when previously abundant rains tapered off during early August and sweltering heat returned shortly thereafter.
A historic cold snap set the tone for a cool September, which saw one of the earliest intrusions of winter weather in state history. An unusually strong cold front blasted through the state September 8-9, sending temperatures plummeting up to 50 degrees lower than the previous day’s highs. Lowest maximum and minimum temperature records were shattered across the western half of the state. High temperatures on the ninth struggled to a chilly 40 degrees at Boise City and Kenton following lows of 33 degrees.
September normally sees at least one or two decent cold fronts to whet the appetite for fall. Mother Nature had different plans this year, however, steering summer right past the beginning of autumn and giving Oklahoma its fourth warmest September since records began in 1895. The Panhandle experienced its warmest September on record, while the north central, southeast, and west central areas of the state had their second warmest. Tulsa ended with their second warmest September on record at 81.2 degrees, 8.2 degrees above normal.
Many of Oklahoma’s most extreme rainfall events have occurred during the fall, the result of a rare conjunction of meteorological ingredients converging over the Southern Plains. Those ingredients – the remnants of a pacific tropical system, a stalled front, and abundant moisture from the Gulf of Mexico – came together late in the month to produce massive rainfall totals across south central Oklahoma. The Oklahoma Mesonet site at Fittstown recorded 14.2 inches of rain on Sept.
Hot and dry weather dominated Oklahoma’s weather headlines for much of September, a drastic change from the extraordinarily mild and wet August the state had just experienced. Many wondered if fall’s premiere would wait until October, but those fears were soon alleviated with the arrival of a strong storm system during the month’s final week. High temperatures in the 50s and 60s along with generous rainfall amounts of 2-4 inches provided a pleasant burst of autumn for much of the state and a welcome bout of moisture for Oklahoma’s wheat farmers.