Shorts and T-shirts are getting extra wear this year as warm temperatures keep students basking in the warm November sun.

Chuck Myers, senior meteorologist with the National Weather Service in Johnston, said the average temperature in Des Moines was 57.7 degrees in October. This is about four degrees above average, a number which Myers said is substantially high.

“We’ve been running above normal for a long time now,” he said, adding the state is seeing unusually high temperatures this fall because the main jet stream has been stuck in the north.

Elwynn Taylor, professor of agronomy, teaches meteorology classes and said there are a number of things contributing to warm weather.

“There is a high pressure system located over the Northeast [of the United States], which brings southeasterly air up to the Midwest, along with the recent rain,” he said. “The jet flow is well up into Canada, keeping the cold air bottled up.”

La Nina may be another cause of the warm weather, Taylor said.

Last winter La Nina played a significant role in the mild temperatures felt across the Midwest.

Taylor said there is not a present state of La Nina, but he said it looks like the weather phenomenon may soon take effect.

“The atmospheric pressure is characteristic of a La Nina,” he said. “The atmospheric pressure is doing exactly what it did last year.”

La Nina has both positive and negative effects on the Midwest, Taylor said.

“With weather extremes there is a chance of extreme storms and precipitation,” he said. “If weather is warm, precipitation can help build up the soil moisture. When soil is frozen it does not make much of a difference because it can’t absorb any of the precipitation. Too much snow then causes floods.”

Myers and Taylor said temperatures are likely to stay above normal this winter.

“The weather service forecast says winter is to be on the mild side, but not quite as mild as last year,” Taylor said. If La Nina does occur, it is likely temperatures would be as warm as last winter, he added.

A common misconception, Taylor said, is the warm weather is due to global warming or the greenhouse effect.

“The influence of humans is detectable,” he said. “But it isn’t the overriding factor.”

Julie Bartels, senior in animal science, is one of the many students who has been enjoying the warm, spring-like weather.

“I really like the warm weather,” she said. “I ride my bike to class, and it is not so bad when it is warm outside.”

Some students like Mike Bandstra, senior in dairy science, are anticipating the cold weather and snow.

“I’m always hot, so I don’t mind the cold weather,” he said. “I don’t like everything about winter though. I hate when the snow melts and it gets all muddy outside.”