June 2012 Weather and Its Impacts on Missouri

Pat Guinan
State Climatologist
Commercial Agriculture/University of Missouri Extension

One of the worst droughts in nearly 25 years was impacting Missouri by the end of June and agricultural crops were feeling the stress from lack of rain and sweltering temperatures. Preliminary precipitation data indicate June 2012 was the 6th driest June on record for Missouri and the driest since 1988. Statewide average June rainfall was less than two inches, or nearly 3 inches below normal. The combined May-June average rainfall for the state was just over 4-inches, ranking it the 6th driest May-June period on record and the driest since 1988.

Extreme heat during the last week of June exacerbated the stressful conditions with many locations reporting triple digit heat and record temperatures. The last time Missouri experienced 100-plus degree heat in June was 1988. On June 28th, several communities reached all-time high temperature records for the month of June including St. Louis, Columbia, Rolla, and West Plains with 108, 107, 106 and 106°F, respectively. The statewide average monthly temperature was about 3 degrees above normal, and will likely rank in the "Top 20" warmest Junes on record for the state.

Similar to May, there were an unusual amount of sunny days during June, and when coupled with above normal temperatures and below normal relative humidity, led to unusually high moisture loss from soils, vegetation and water surfaces - a process known as evapotranspiration. June average relative humidity for the state ranged from 55-60%, and was the lowest for the month since June 1988. These conditions, in combination with lack of rainfall, resulted in a rapid increase of agricultural impacts due to drought stress. Reports of deteriorating pastures, declining soil moisture reserves, limited stock water supplies, and crop stress increased as June progressed. Un-watered lawns quickly turned brown and irrigation went at a record pace. Several automated weather stations across the state reported short crop evapotranspiration rates exceeding 0.25"/day, and totals were around 7 inches for the month.

Grass fires increased during June and burn bans were imposed across the state. Toward the end of the month, a forest fire in the Mark Twain National Forest burned 600 acres in Iron County and was believed to have been deliberately started. Another forest fire, initiated when a mower blade struck a rock and threw sparks, burned 48 acres in Madison County.

According to the Missouri Agricultural Statistics Service, by the end of June, 97% and 93% of the topsoil and subsoil moisture supplies, respectively, were in short to very short condition. Nearly half of the corn and soybean crop was reported to be in poor to very poor condition, and is the highest percentage for the time of year since 1988. Pasture condition had declined to 76% poor to very poor, and hay and stock water supplies were also declining with more than half in short to very short condition.

Historically, a dry May-June period does not bode well for Missouri. Looking at the "Top 15" driest May-June periods on record for the state, and what happened the following July, 60% of the Julys were hotter than normal, 27% were cooler than normal, and 13% were near normal. For precipitation, 73% of the Julys were drier than normal, 13% were wetter than normal, and 13% were near normal.

Despite a relentless drought, the state was not devoid of severe weather. On June 4th, an EF-2 tornado tore through the southeastern community of Diehlstadt, in Scott County, and killed a father and his two sons in a mobile home that was destroyed beyond recognition. A National Weather Service survey determined the tornado was about 75 yards wide, on the ground for 0.5 miles and had peak winds of 115 mph.

With drought and extreme temperatures persisting at the end of the month, and a hot and dry forecast for July, there is a distinct possibility this year will transition from a "1988-like" spring drought to a "1980-like" July heat wave and drought for Missouri.