Summer in September: New climate trend or not so unusual?

If the hot, dry September has you standing in line for ice cream instead of warm pumpkin spice lattes, you’re probably not alone.

The immediate cause for the midsummer temperatures is an area of high pressure overhead, which promotes the current dry, summer-like weather, according to the U.S. National Weather Service Facebook page.

Is this weather an anomaly? No, although recent temperatures in northern Illinois are “on the high side of average,” said Kevin Birk, a meteorologist at the U.S. National Weather Service in Romeoville.

Will hot Septembers become routine? Probably, said Nancy Kuhajda, a University of Illinois Extension horticulture educator serving Grundy, Kankakee and Will counties.

Birk said it’s not unusual for temperatures to climb into the 80s and low 90s in the early parts of September.

“We did have some cooler weather in August,” Birk said, “and a taste of fall on the 7th of September with only a high of 67.”

“Normal temperatures for this time of year are in the mid-70s,” Birk said. “We’re about 10 degrees above average.”

Saturday should be the last day in the 80s, Birk said. A chance of rain is in the forecast over the weekend.

“Certainly, with the climate warming, we’ll see more of these types of events,” he said. “But I wouldn’t say that’s necessarily going to be the new normal around here.”

Climate changes in plant life

Kuhajda said people have observed climate change ever since they began tracking climate, and evidence can be found in nature that things are shifting.

After 40 years of tracking when plants bloomed in various parts of Illinois, experts are finding accelerations.

“So, we are warming up,” Kuhajda said.

For instance, the “hardiness zones” on plant tags have changed, Kuhajda said. When Kuhajda started working for the Illinois Extension in 1982, northern Illinois was Zone 5. It’s now Zone 6, she said.

Certainly, with the climate warming, we’ll see more of these types of events. But I wouldn’t say that’s necessarily going to be the new normal around here.”

—  Kevin Birk, meteorologist at the U.S. National Weather Service

Butterweed, a large, daisy-like flower that was common in southern Illinois, is moving north, Kuhajda said. Some plants that are annuals in northern Illinois are becoming perennials because temperatures are not “dipping low enough for long enough,” she said.

The Blue Victorian Salvia, the Dusty Miller, and even the tropical cannas that must be dug up in the fall and overwintered in the house are coming back every year when left in the ground, Kuhajda said.

But does it really matter if forsythias are now blooming in March and lilacs blooming in April instead of mid-May?

Yes, Kuhajda said, it matters to pollinators – such as monarchs – that rely on certain plants for food. When plants bloom early, they stop flowering early.

“Look at the roadside plants, goldenrod and asters,” Kuhajda said. “They’re at the peak of bloom now and will probably finish by the end of September. What are those pollinators going to eat?”

The monarchs may move into Canada for food – and then travel 4,000 miles to Mexico instead of 3,500, she said.

“We had a very low butterfly summer,” Kuhajda said. “We’ve been literally down to single digits in observations of monarchs; people haven’t seen many. And we hardly saw any caterpillars.”

Dry weather often brings drought, underscoring the saying that “water is the new oil,” Kuhajda said. Ironically, polar vortexes occurring over recent winters signal global warming because warming temperatures will push “super cold Arctic air” south, she said.

“The problem here is now we have a warming climate,” Kuhajda said. “And then we have this sudden influx of super cold air, which can be really harmful to nature.”