I've been seeing some leaves change colors already and it got me thinking about fall, of course! This is early for leaves to change in these parts - this is a map of where the leaves are changing color around September 17th.
I always think it's so interesting (and beautiful!) when the leaves change color. Here's an explanation of why (with help from the College of Environmental Science and Forestry at the State University of New York) -
During the summer and spring the food-making process is in full swing among the leaves. This happens in the leaf in numerous cells containing chlorophyll, giving leaves their green color.
In the fall, with changes in the length of days and the cooler temperatures, leaves stop this food-making process. The chlorophyll breaks down, the green color disappears and the yellow to orange colors become visible. Other chemical changes may happen, which leads to additional colors like red and purple.
Temperature, light, and water supply influence of the degree and duration. Low temperatures above freezing will favor producing bright reds. Early frost will weaken the bright reds. Rainy or overcast days tend to increase the intensity of fall colors.
The fall colors in my neck of the woods start to intensify in mid-October and peak later on in the month. Here's the map around October 29th.
It's always hard to tell exactly how the colors will go each year. In the short term we have some pretty warm weather still, but there will be a change late in the week to some more fall-like weather. In all, temperatures are going to run near and above normal through the end of the month.
There will be periodic thunderstorm chances as well starting on Tuesday. The expected precipitation looks something like this across the Upper Midwest:
There may be some heavy rain in parts of Iowa and Minnesota, but something to watch with each round that comes through.