September 23, 2010

Record High Humidity Makes 2010 Summer Uncomfortable

Humidity, as well as high temperatures, played a big part in the uncomfortable summer of 2010, said a University of Missouri climatologist.

A combination of high humidity and high temperatures results in a high heat index. This summer we had the most hours of heat indices over 100 degrees in more than a decade, said Pat Guinan of the MU Extension Commercial Agriculture Program.

Preliminary data shows the average dew point in Columbia this summer was 69 degrees, which makes it the highest since observations were first digitized in 1948. Dew point is the temperature at which moisture condenses out of the air.

When air contains high moisture content, the temperature doesnt have to drop much to start condensation. High dew point readings this summer led to morning dew on grass, fog, wet pavements and that clammy feeling.

Temperatures were also higher than average. For the state, the overall average summer temperature was 78.5 degrees. That was 3.1 degrees above normal for June, July and August, Guinan said. Preliminary numbers indicate it was the ninth-hottest summer on record and the hottest since 1980.

Nighttime temperatures were higher as well. Columbia had only 12 days during that three-month period when minimum temperatures fell below normal. The average minimum temperature was 68.3 degrees, or 4.3 degrees above normal.

The records confirm what most people know: It was an uncomfortable summer.

Summer rainfall was variable across the state, Guinan said. Average for June was 4.59 inches and for July was 6.59 inches. August averaged 2.75 inches, about one inch below normal.

The statewide combined summer rainfall average was 13.93 inches, 2.14 inches above normal, to make it the 28th wettest on record. However, Hannibal had the wettest summer on record with 27.5 inches.

In August, drier conditions prevailed. Caruthersville, deep in the Bootheel, reported no precipitation for the entire month. Heaviest rainfalls of 3-5 inches were recorded over central Missouri.

Regionally, the rainfall was extreme. June through August rainfall totaled over 29 inches in Kahoka in far northeast Missouri and only 3.1 inches total at Kennett in the Bootheel. Drought prevailed across south-central and southeastern sections for much of the summer, Guinan said.

The three-month outlook through November from the National Weather Services Climate Prediction Center calls for above-normal temperatures and below-normal rainfall across most of Missouri. However, the northwest part of the state has an equal chance of above-normal, below-normal or normal rainfall.

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