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July Provides Fall Preview

Mother Nature threw Oklahoma a Hail Mary during the final week of July, offering drought-quenching rains and a glorious preview of fall. That brief seasonal transformation followed a dose of brutal summer weather that saw highs soar above 110 degrees and the heat index hit 120. The middle two weeks were especially fierce, culminating with record-breaking heat from the 19th through the 22nd. Temperatures reached 113 degrees at the Grandfield and Tipton Mesonet sites on both the 19th and 20th. There were 35 instances of temperatures reaching at least 110 degrees at Mesonet sites during the month, and highs reached 105 degrees 93 times. Combined with the humidity, the heat became even more oppressive. The heat index soared to 120 degrees at Pawnee on the 19th and again at Bristow the following day. The Mesonet’s 120 sites recorded heat index values of at least 115 degrees 36 times during July. The cold front that visited the state during the month’s final week was unusual in both its timing and strength, but provided a welcome respite from Oklahoma’s normal July drudgery. Rainy weather, clouds and the cooler air helped provide Oklahomans with a brief glimpse of fall. Highs struggled to reach 90 degrees, and Boise City and Eva fell to a relatively chilly 50 degrees on July’s final day. According to preliminary data from the Oklahoma Mesonet, the statewide average temperature for July was 81.2 degrees, 0.3 degrees below normal and ranked as the 58th coolest since records began in 1895. The year-to-date temperature through July was still very warm at 0.8 degrees above normal, the 29th warmest January-July on record.

 

The real benefit of the late-month cold front was the moisture it brought to a parched state. Through July 26, the statewide average rainfall total according to the Oklahoma Mesonet was 1.28 inches, on pace for the 21st driest July on record. That statewide average had more than doubled over the next five days to 2.93 inches, upping its ranking to the 57th wettest on record. The heaviest rains fell across far northern Oklahoma and localized areas in the east. Twenty-Two Mesonet sites reported at least 4 inches of rain, with Pryor leading the state at 6.09 inches. Not all sections of the state were so fortunate, however. Significant deficits remained along the Red River as well as portions of north central Oklahoma. Ringling recorded 0.84 inches of rain for the lowest July total, while another 27 Mesonet sites recorded 2 inches or less. The first seven months of the year finished 2.53 inches below normal to rank as the 51st driest January-July on record. As with the monthly totals, the year-to-date totals were also highly variable. Southwestern Oklahoma was 6.23 inches below normal for their 18th direst such period, while east central Oklahoma enjoyed its 43rd wettest at 1.25 inches above normal. Deficits of nearly 10 inches existed over that period from southwestern through northeastern Oklahoma. Hollis received 7.5 inches of rain since Oct. 1, 2017, a deficit of 13.2 inches.

 

Despite the late relief during July, the U.S. Drought Monitor ended the month with 55 percent of the state in drought, and another 12 percent considered “abnormally dry,” a drought precursor. Thirty-Two percent of the state was in at least “severe” drought, and 7 percent was labeled “extreme.” Extreme drought dropped 5 percent since the end of June, but severe drought increased 9 percent. The Drought Monitor’s intensity scale slides from moderate-severe-extreme-exceptional, with exceptional being the worst classification.

 

The August temperature outlook from the Climate Prediction Center (CPC) indicated increased odds of above normal temperature for all but the extreme northeast corner of the state. Those odds were greater along the Red River. The precipitation outlook saw slightly increased odds for below normal precipitation across the southern half of the state, but no clear signal in the northern half. Drought is expected to persist or intensify along the Red River and in the far western Panhandle during August, according to CPC’s Monthly Drought Outlook. Other areas that were in drought at the end of July can expect improvement by the end of August.