El Niño is affecting Michigan’s weather, causing leave to change colors later. Sophia Mandt | Collegian

Southern Michigan’s fall leaves are predicted to change colors later than usual this fall.

Last year, Hillsdale had almost full leaf drop by November 1, according to Jason Blake, director of the City of Hillsdale’s Department of Public Services.

“I believe the color change has been pushed back by a week or two,” Blake said. “The full fall leaf drop has moved back a couple weeks over the last few seasons.”

Blake said the change is causing challenges for DPS crews picking up leaves.

“Due to the leaf drop almost all at once, DPS crews get a week or so behind in the last two wards of round one of two pickups, and we anticipate the same this year,” Blake said. “When we are behind, two crews will be sent out in an attempt to stay on schedule.”

Blake said the Department of Public Services finished a week behind schedule last year, on December 9.

But why the warming temperatures? It’s likely thanks in part to a weather phenomenon known as El Niño.

Christopher Heckel, Assistant Professor of Biology explains that El Niño affects the Midwest even though it results from shifting wind currents and wind patterns in the Pacific Ocean.

“Normally what happens is warmer equatorial waters from South America get warmer, and the easterly trade winds blow that warm water across the Pacific towards Indonesia, creating a need for the cooler water to flow up as part of the water cycle.”

Heckel said that when these trade winds weaken, it has a domino effect on other patterns, ultimately affecting weather in the Midwest.

“What El Niño does for us here in the Midwest is give us dryer and warmer winters,” Heckel said.

Because the weather in Hillsdale Country has been slightly warmer than expected from El Niño, the fall colors in Hillsdale Country are anticipated to change later this season.

Heckel said that the trees are metabolically shutting down.

“As winter approaches, the days become shorter and trees are unable to perform as much photosynthesis, and so they’re starting to produce less chlorophyll, the pigment that makes the leaves green,” Heckel said. “The other pigments contained in the leaves become more visible on the surface of the leaf.”

Heckel said the most important factors affecting fall leaf colors are day length, moisture, and temperature.

“The temperature from warm summer days in the late summer to early fall compared with cool, crisp nights gives the best fall colors as the leaves are still able to have good sugar production from the daylight warmth,” Heckel said.

Predicting when the fall leaves will change colors is far from an exact science, State Urban Forestry Coordinator for the Michigan Department of Natural Resources Kevin Sayers said.

“It’s partly because it’s linked to the variability in weather conditions and site conditions around the state,” Sayers said. “Like weather forecasting, it’s often inexact as to the area and the timing but typically it follows pretty recognized trends.”

Sayers said soil moisture affects fall colors.

“If it’s been dry, that is a stress, and plants that are stressed tend to exhibit indications of that in the color of their leaves. So if you’ve had a dry fall then that may be manifested by earlier fall colors.”

Sayers also said trees that get more sun exposure typically have more vibrant colors.

“In a very general sense you can ballpark where and when other trends are going to peak based on watching the weather, temperature, and locations around the state,” Sayers said.

“For example, we know intuitively that the Upper Peninsula is going to start getting colder with less light earlier in the fall than the southern parts of the state.”

Sayers said that while the timing is very tied to the weather conditions, the southern part of the state around Hillsdale County will probably reach peak fall colors close to Halloween.

“Get out and take it in, and appreciate it,” adds Sayers.

“Michigan is a great state for fall color whether you’re in the Upper Peninsula or or in the lower part of the state. You’re going to see beautiful fall colors. Just open your eyes, get outside, take it in. Enjoy it.”