SUMMER GOES INTO RECORD BOOKS; AUGUST WEATHER CONTINUES ABOVE-NORMAL TEMPERATURE TREND

The summer of 1991 went into the record book here as warmer, but less humid than normal.

The lower humidity levels made it seem somewhat more pleasant than most typical Southeast Missouri summers in this area, according to Al Robertson of the Earth science department at Southeast Missouri State University.

Robertson said the average temperature for the period June 1 to July 31 was 79.2 degrees, up 1.6 degrees from the long-term, three-month average of 77.6 degrees.

For purposes of weather statistical reporting, Robertson explained, the National Weather Service and climatologists have classified the four seasons spring, summer, fall and winter into 90-day segments.

The weather service recognizes summer as the months of June, July, and August. Of course, by the astronomical calender, summer begins in late June and ends in late September.

Robertson said the summer of 1991 in Cape Girardeau was the sixth warmest in 45 years. The warmest summer ever here was in 1980, with an average temperature of 80.9 degrees. The second warmest summer was in 1952, with an average of 80.8 degrees.

"It was just downright hot most of the summer," said Robertson. "Usually, each month had about 10 to 11 days of hot weather, then it would cool off for a while, and warm up again. It was the old roller-coaster routine."

Despite the heat, the temperature failed to reach the 100-degree mark this past summer, although it came close several times.

The high for the three-month period was 99 degrees, on July 1. On Aug. 4, the high reached 98 degrees. There were several other days during the period when the temperature peaked at 97 degrees.

Despite the warm weather, Robertson said the heat didn't seem as oppressive during much of the summer because day- and nighttime humidity levels remained generally lower than normal for this area.

"Typically, we would expect to see humidity levels go up during the first part of July and continue through all of August," said Robertson. "But this year was different. High level winds kept the very humid air from the Gulf of Mexico well to the south of us most of the summer."

The result, said Robertson, was sunny, hot days, but clear, cool nights. He said the low humidity allowed heat in the atmosphere to radiate back into space at night, resulting in morning lows in the mid-to-upper 60s and low 70s.

Robertson said the upper air patterns also permitted some intrusions of cool, dry air from Canada during the period, providing relief from the hot, dry weather.

On Aug. 20, for example, the morning low dipped to 56 degrees, which marked the low for the month and for the summer.

For the 17-day period from Aug. 8-25, the morning lows were in the 60s, except for a 70-degree reading on Aug. 17.

But the mild weather came to an end Aug. 30 as very humid Gulf air arrived, keeping morning lows in the sultry 70s through the first half of September.

Rainfall during the summer months was below the long-term average, Robertson said. Total precipitation for the period was 8.82 inches, compared to the long-term average of 10.76 inches.

"June was very dry, with only 1.05 inches of rain. July was also drier than normal, with 2.93 inches," said Robertson. "August rainfall was above normal, but the figure is misleading."

Robertson explained that Mid-America Weather Services' rain gauge at the Cape Girardeau airport recorded 4.84 inches of rain during August, about one inch above the long-term average. But Robertson pointed out that nearly half of that amount did not fall in Cape Girardeau.

"The rainfall pattern in August was extremely spotty. Some areas got lots of rain, others got very little," he said. "A good example is Aug. 5 when a thunderstorm passed over the airport and dropped 2.12 inches of rain. In the city, we got less than a half inch."

Robertson said August was the seventh consecutive month this year with above average temperatures. Only January was slightly cooler than normal.

"August started out hot, then cooled down in the middle, and heated up again toward the end of the month," he said. "There were 15 days when the high was 90 or above, but the very mild weather in mid-month kept the overall monthly average down to 78.1 degrees, which was just .07 of a degree above the long-term average."

Robertson said the 10-day average for Aug. 1-10 was 81 degrees, up 2.6 degrees from the long-term average. But the 10-day average for Aug. 11-20 dropped 2.6 degrees from the long-term average, to 74.8 degrees.

Through Aug. 31, precipitation at the airport for the year totaled 28.48 inches, compared to the long-term average of 30.79 inches. "That's not bad for the first eight months," he said. "We're still down about 7 percent, or 2.31 inches for the year, but keep in mind the precipitation pattern has been widely scattered. If the airport or the city rain gauges had been moved just a few miles in either direction from their location, we would have some totally different statistics."

For the first 16 days of September, rainfall at the airport stood at 1.54 inches.

In its 30-day, mid-September to mid-October weather outlook, and 90-day outlook through the end of November, the National Weather Service says temperatures and rainfall in this area will be around seasonal levels.