July 2018 Climate and Hydrology Summary

July 2018

Tulsa: July 2018 was the 40th warmest (83.9°F, tied 1937, 1913; since 1905) and the 60th wettest (2.70"; since 1888) July on record.

Tulsa: Daily records set or tied this month include a record minimum temperature.

Fort Smith: July 2018 was the 18th warmest (84.7°F; since 1882) and the 61st driest (2.31", tied 1898; since 1882) July on record.

Fayetteville: July 2018 was the 33rd warmest (78.4°F; since 1950) and the 19th wettest (4.31", tied 2008; since 1950) July on record.

Using the radar-derived estimated observed precipitation from the RFCs, rainfall totals for July 2018 ranged from around 1.5” to isolated amounts around 7” across eastern OK and northwest AR. The highest rainfall totals were primarily across far northeast OK and northwest AR and Le Flore County in southeast OK. This corresponds to 25-200% of the normal July rainfall scattered around eastern OK and northwest AR.

There was a mix of above and below normal rainfall across eastern OK and northwest AR this month, as can happen with typical summertime convection.

At mid-month, several upper-level troughs in a northwest flow pattern, combined with summer time heat and a moist axis, resulted in several days of scattered showers and thunderstorms. While most affected areas received around 0.75” or less, isolated locations saw 2”-3”.

A change to a ridging pattern resulted in the hottest temperatures of the year so far. High temperatures climbed into the upper 90Ëšs to low 100Ëšs across eastern OK and northwest AR on the 19th, and combined with the dewpoint, heat index values were 105Ëš-120Ëš. Several record high temperatures were then set on the 20th, with high temperatures exceeding 100Ëš across all of eastern OK and northwest AR except far northern OK near the state line. Heat index values reached 110Ëš-120Ëš.

Scattered showers and thunderstorms developed over eastern OK and northwest AR throughout the day on the 29th and then dissipated with the loss of daytime heating. A mesoscale convective system (MCS) moved southeast out of KS and into the region during the early morning hours of the 29th. The line of storms moved quickly southeast, bringing rain to all of eastern OK and northwest AR, before shifting east of the area shortly after noon. Another MCS developed slightly further west overnight and affected primarily eastern OK and west central AR during the morning hours of the 30th. A smaller thunderstorm complex moved south out of KS into northeast OK during the afternoon, affecting northeast and east central OK and northwest AR during the afternoon and evening hours. Rainfall from each round of storms generally ranged from around 0.50” to around 3”.

According to the Drought Monitor from July 31, 2018, Extreme (D3) Drought conditions existed over northern Craig, southern Pushmataha, and Choctaw Counties in eastern OK. Severe (D2) Drought conditions were impacting Osage, northern Pawnee, Washington, northern Tulsa, Nowata, Rogers, Craig, Ottawa, Pushmataha, and Choctaw Counties in eastern OK. Moderate (D1) drought conditions were present across portions of Osage, Pawnee, eastern Kay, Washington, Tulsa, Craig, Ottawa, Rogers, Mayes, Delaware, Cherokee, and Pushmataha Counties in eastern OK, and Benton, Carroll, Washington, Madison, Crawford, Sebastian, and Franklin Counties in northwest Arkansas. Abnormally Dry (D0) but not in drought conditions encompassed portions of Pawnee, Creek, Tulsa, Okmulgee, Wagoner, Cherokee, Adair, Sequoyah, Muskogee, Haskell, Le Flore, and Pushmataha Counties in eastern Oklahoma and Sebastian County in west central Arkansas.

According to the Oklahoma Climatological Survey, July 2-31, 2018 was the 49th driest for northeast Oklahoma, the 48th wettest for east central Oklahoma, and the 46th driest for southeast Oklahoma. Records go back to 1921. For the Year-to-Date period Jan. 1-July 31, 2018, northeast Oklahoma ranked as the 22nd driest, east central Oklahoma was the 27th wettest, and southeast Oklahoma was the 35th wettest period. For the last 365 days (Aug 1, 2017-Jul 31, 2018), northeast Oklahoma was the 39th driest, east central Oklahoma was the 41st wettest, and southeast Oklahoma was the 47th driest.