Cool with this weather?

If you've resisted putting away your summer clothes, give up.

Below-normal temperatures are expected for most of the remaining few weeks of “summer” and, possibly, through fall.

Given the likely chillier weather, an early freeze is possible, meteorologists say.

That would bring some bad news — an abrupt end for tender annual flowers and the corn crop's maturation — but also some good news with an early end to hay fever season.

Nebraska has seen one of its coolest summers on record, according to the National Weather Service.

It's been the fifth-coolest in Norfolk; the sixth-coolest in Kearney; the seventh-coolest in Grand Island, Hastings and North Platte; and the 10th-coolest in Omaha. City records are based on varying time periods from the early 1870s to early 1900s.

But a cool summer and fall don't automatically lead to a bitter winter, meteorologists say.

Because climatic conditions known as “El Niño” are occurring in the Pacific Ocean, meteorologists are projecting a warmer and, with less certainty, drier than normal winter for the region.

“It sure feels like it will never warm up,” said Barbara Mayes, meteorologist with the National Weather Service office at Valley. “But we are fairly confident in a prediction of warmer than usual weather for winter.”

The key to winter will be the future strength of the El Niño that formed in July, said Michelle L'Heureux, a meteorologist at the Climate Prediction Center in Camp Springs, Md., a sister agency to the National Weather Service.

El Niño is a global weather phenomenon that occurs when the waters of the central and eastern Pacific Ocean are warmer than normal. Those warm waters send a tremendous amount of moisture and energy into the atmosphere, creating shifts in weather.

Currently, the ocean is in a weak El Niño phase that is forecast to strengthen this winter, L'Heureux said.

If that happens, the El Niño could block some of the Arctic air that would otherwise flood down into the Plains. That, she said, would be the mechanism that would lead to a warmer than normal midwinter.

However, there's no guarantee that El Niño will strengthen and block Arctic air. If it doesn't, a prolonged period of cold could lie ahead.

“We're lucky this is an El Niño year, otherwise we'd be staring down the face of a very cold winter,” said Ken Dewey, applied climatologist at the University of Nebraska-Lincoln. “The odds (for a warmer than normal winter) remain with us.”

Although an early freeze might sound ominous to gardeners, the ongoing cool weather has been preparing plants for that possibility, said Kathleen Cue, horticulturist for the University of Nebraska Extension in Douglas and Sarpy Counties. That should help lessen the shock of a freeze. If temperatures had been higher than normal, an early freeze would be a bigger threat, she said.

The early cool weather won't hasten the arrival of fall colors, said Rich Lodes, a forester with the Platte South Natural Resources District and Nebraska Forest Service.

Instead, trees are waiting for the shortening days to signal it's time to change colors, he said.

Each species of tree follows its own schedule, Lodes said. Sumac is changing now; ash and cottonwood will follow, and oaks won't take on their color until about November.

Lodes said the weather conditions shortly before leaves change color determines their brilliance. Sunny and cool weather typically trigger the best fall colors, he said.

“We're having fall-like weather, but our leaves aren't changing because they're not having the proper cue from daylight,” he said. “You can't separate one from the other.”

Contact the writer:

444-1102, nancy.gaarder@owh.com

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