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. The gray, rainy weather managed to avoid southeastern Oklahoma, leaving that area of the state stuck in summer mode for a bit longer. Eastern Oklahoma saw dry conditions expand through the end of the month as drought tried to mount a comeback.
According to preliminary data from the Oklahoma Mesonet, the statewide average precipitation total was 2.60 inches, 0.93 inches below normal and the 50th driest September since records began in 1895. The statewide average failed to reflect the stark difference in rainfall amounts across the state, however. Much of the eastern third fell 3-4 inches below normal. Southeastern Oklahoma saw its driest September on record with an average of 0.45 inches, 3.82 inches below normal. The previous record low total of 0.57 inches was set during the significant drought years of 1931 and 1956. Parts of east central and south central Oklahoma experienced similar deficits. The Panhandle averaged 3.34 inches, 1.52 inches above normal to rank as their 16th wettest September. West central and southwestern Oklahoma also saw a significant moisture surplus. The Mesonet sites at Cloudy and Hugo reported no rainfall for the month, and another six had a tenth of an inch or less. Grandfield recorded 9.87 inches to lead the state, a whopping 7.1 inches above normal. Of the 121 Mesonet sites, 46 recorded at least 3 inches of moisture. The year through September remained significantly wet with a statewide average of 33.52 inches, over 5 inches above normal and the 13th wettest such period on record.
The state registered its last triple-digit temperature of September – and possibly the year – on the 21st with Beaver, Buffalo and Cherokee hitting 100 degrees. The heat was not over yet, however. While the northwestern half of the state cooled down a few days later with the arrival of the large storm system, the rest of the state continued to bake. The heat index rose to as high as 97 degrees on the 27th in Idabel in the far southeast. During that same period, highs across western Oklahoma were in the 50s and 60s. That final week’s brush with milder air was enough to bring the September statewide average down to a more respectable 72.9 degrees, 0.6 degrees above normal. The month’s highest temperature of 101 degrees occurred at several sites on two separate days. Triple-digit temperatures were uncommon, however. The 121 Mesonet sites reached 100 degrees a mere 10 times during September. The January-September statewide average of 65.1 degrees was 1.7 degrees above normal, the 16th warmest such period on record.
Oklahoma was drought free at the beginning of the month, and only 2 percent of the state was considered “abnormally dry” by the U.S. Drought Monitor. While not a drought designation, abnormally dry can indicate areas where drought development is likely. September’s last Drought Monitor report listed 33 percent of the state in abnormally dry conditions and a little less than 1 percent suffering from moderate drought.
The Climate Prediction Center’s (CPC) October outlooks indicate increased odds for below normal precipitation across the southeastern half of the state, especially in far southeastern Oklahoma, and increased odds of above normal temperatures over all but the northwestern quarter. Accordingly, CPC’s October U.S. Drought Outlook has drought development being likely across far eastern Oklahoma.