Sizzling July melts records as hottest on record in Salt Lake

Next time Grandpa claims he had to walk farther to school and that the weather in the old days was worse, tell him the school part might be true but he's wrong about the weather.

Last month was the hottest on record in Salt Lake City since the National Weather Service began tracking the temperature in 1928. The average temperature was 84 degrees. Many triple-digit thermometer days contributed to the high averages.

According to Brian McInerney of the Weather Service's Salt Lake City office, meteorologists record each day's high and low temperatures. When these are added together and divided by two, the answer is the day's average temperature.

When the average temperatures for each day of the month are added and divided by the number of days in the month, the result is the monthly average temperature.

McInerney said the previous high average July temperatures were in 2003, at 83.4 degrees; 2006, 83.1; and 2002, 81.9.

"And then you go back to July of 1960 at 81.2 degrees Fahrenheit," he said. This means that four out of the all-time hottest July averages were in this decade.

"We know the climate is warming," McInerney said. "That's been recorded, and this would fall right in with it."

Besides climatic warming, what factor could be causing this?

"It's called persistence," he said.

Persistence, in meteorological terminology, is "when you have a weather pattern set up and it stays that way for quite a long time," he said.

"The persistent weather pattern for July in Utah was a high pressure parked over the state." The high pressure system prevented storms from forming in this area.

At the same time, in Texas "they had the coldest July on record, and they had flood issues for almost the entire month."

In Utah, McInerney bemoaned, "we couldn't even buy a cloud."

The pattern that formed and persisted caused excessively toasty temperatures because no clouds blocked the sun's rays and rain wasn't falling to cool the air.

"Now," he said, "we've kind of changed out of this."

After the prolonged heat wave, parts of the state are being soaked by intense rainfall, he said. High waters on the Virgin and Santa Clara rivers were of the type that happen only about once in five years, and the state also had some of the biggest flash floods of recent times.

Weather persistence seems to be happening again, this time with storms. "The system set up," McInerney said, "and it just kind of parked again."

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E-mail: bau@desnews.com