While much of Earth baked in July, Nebraska stayed cool

August 27, 2018

While much of the world baked in July — and some areas burned — there was a nice little cool spot in the heart of the U.S. — Nebraska.

Nebraska was the only state in the U.S. to be classified as noticeably cooler than average that month, and it was among those areas of the globe that ran counter to the planetary average by being on the cool side.

Good thing, too.

Nebraska’s mild July weather — the statewide temperature averaged 73.4 degrees — gave the landscape a chance to recover from the extreme heat that occurred at the end of spring and start of summer (Omaha notched its earliest back-to-back days of triple-digit temperatures in May, 100 degrees and 101 degrees on May 26 and 27). This better guaranteed that gardens would become productive and that late-flowering plants would still blossom, said a local horticulture educator.

“It was a blessing that it did cool down and allow plants to recover,” said Scott Evans, a horticulturist with Nebraska Extension in Sarpy and Douglas Counties. “Hopefully, extreme heat won’t be the norm, but the climate is changing.”

Evans credits that milder July weather for the tomatoes, squash and zucchini that people are now enjoying. Pollen can become sterile once temperatures climb above 90 degrees, he said, which meant that blossoms weren’t setting fruit early on. “The cooler weather allowed the pollen to be fertile,” he said.

Nebraska had its 40th-coolest July out of 124 years in the national records. It was part of a corridor of coolness in the upper Great Plains and Canada. Other areas of the planet that were noticeably cooler than average included southern South America and northern Asia.

In contrast, the U.S. had its 11th-warmest July on record, and the planet experienced its fourth-warmest July. California saw record heat and massive wildfires. Death Valley recorded the planet’s hottest average monthly temperature —108.1 degrees.

So why was Nebraska the odd one out?

Associate state climatologist Al Dutcher said there were two primary reasons:

Cool Canadian air. Nebraska was perfectly situated to benefit from a trough of cool air that dropped down from Canada.A monsoonal flow out of the southwest U.S. Moisture from the monsoonal flow limited how much temperatures could rise, and the clouds it generated also helped keep the area cool. (Moisture limits temperature increases because the water absorbs energy that would otherwise go toward making the atmosphere hotter.)

Despite the milder weather of July, plants are still stressed from the heat that occurred in May and June, Evans said. That can be seen, for example, in insect damage to asters.

The plants were stressed by the heat, and bugs, sensing that, are moving in.

“It’s been a challenging growing season,” he said.

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