The rainfall total since May 1 remains the third-driest on record for Columbia, with only 4.71 inches since May 1, according to a report released by the National Weather Service on Aug. 22.

This year in Columbia also ranks as one of the highest in average temperatures between Jan. 1 and Aug. 22.

National Weather Service spokesman Mark Fuchs said droughts are difficult to compare over the course of history because of the variety of factors involved.

“Every drought is unique,” he said. “There are lots of nuances with each one.”

Columbia’s current drought has been ranked a D3, or “extreme drought,” with major crop and pasture losses, extreme fire hazards and widespread water shortages. Many water restrictions have been imposed for conservation purposes.

The intense heat began in June and has exacerbated the drought and lack of rainfall, which began at the start of May.

However, MU atmospheric science professor Anthony Lupo said the drought truly began last summer with extreme heat and the large amount of evaporation, which carried much of the moisture out of the ground.

“Evaporation is a cooling process,” he said. “That energy is taken up by water instead of being injected into the atmosphere.”

Lupo said this extreme evaporation caused the soil to dry up. Heat at the surface of the earth was transmitted to the air, which produced an area of high pressure above the central U.S.

The consistent area of high pressure initiated the drought and above-average temperatures experienced by Missouri and central and southern Illinois.

This increase in pressure also decreases the number of clouds and thus total precipitation, Lupo said.

The National Weather Service report stated the ridge of high pressure remains approximately 20,000 feet above sea level, interfering with the regular patterns of storms that travel across this part of the U.S.

Lupo said a drought is a process, and once that process has started, it is a difficult cycle to break.

“It’s a feedback process that keeps building on itself,” he said. “There’s a famous saying that describes this perfectly: ‘Drought begets drought.’”

The lack of rainfall, coupled with extreme temperatures, has also caused soil and vegetation to dry out, triggering an increased fire risk, according to the report.

The report warns citizens of Columbia to take caution with the use of cigarettes, matches, lighters and any other open flames.

“It’s very, very hot and dry,” Fuchs said. “That took whatever moisture was in the ground.”

Lupo said the consequences of the drought on vegetation and livestock may not be obvious to consumers until next spring.

“It has affected a lot of people in Missouri,” he said. “It has given a huge hit to the agricultural community. We can expect higher vegetable prices and higher meat prices.”

Forecasters from the National Weather Service estimate that the remains of Hurricane Isaac will provide much-needed rainfall to the area this weekend. Forecasters expect 6 to 12 inches of rainfall in the next 30 days, eliminating the drought, according to the report.

Lupo, on the other hand, said he expects the drought to continue for a while.

“Once the rain goes away,” he said, “it will be back to the heat.”