The question was asked as to what weather conditions make for a good color season. So as we begin to turn our attention to fall campfires, cool nights and hopefully some spectacular fall color displays. So what makes for good fall color? Here in Michigan the abundance of hardwood forested landscapes with a mixture of maples, oaks, and beech trees, which produce vivid orange, yellow and red colors. A factor in the fall color display that is not so obvious is the weather leading up to the shortening of the days, which is the cue for leaves to produce less chlorophyll and begin the fall show of color before losing their leaves for winter.
So why do leaves change color? Leaves change color mainly in response to the decrease of daily sunlight. Photosynthesis, or the production of sugars that depend on sunlight, begins to slow down in response to the change in the amount of light. This leads to a reduction of chlorophyll, the pigment that supports photosynthesis and gives leaves their green color. The extent of red color and length of time leaf color is displayed is directly related to temperature and moisture conditions that occur before and during the period when the amount of chlorophyll in the leaves is diminishing.
The role weather plays in the color change. The most brilliant leaf displays follow a period of warm days filled with sunshine and cool nights. During this weather cycle, leaves produce an abundance of sugars during the sunny days. The cooler nights and gradual narrowing of leaf veins in the fall, means that a majority of the sugars produced are trapped in the leaf. An abundance of sugar and light in the leaf lead to the production of vivid anthocyanin pigments, which produce red, purple and crimson colors. Yellow and gold leaf colors are produced by carotenoid pigments, which are ever-present in the leaves and are therefore less dependent on the above conditions. Soil moisture also plays a role in the timing and brilliance of leaf color. The best displays are produced when the soil has been adequately moist throughout the year coupled with the above summer weather. A late spring, or severe summer drought can delay the onset of color. A warm period during the fall can also decrease the intensity of fall colors by triggering early leaf drop before the colors have had a chance to develop.
Some other factors also cause leaves to change color early. Trees in a low-lying areas, where cooler air collects at night, often display colors sooner than trees in an higher area. Trees that are diseased and in decline may also display fall colors earlier than more healthy trees
However, the timing of color changes and the onset of falling leaves is primarily regulated by the calendar as nights become longer. None of the other environmental influences – such as temperature, rainfall, food supply – are as unvarying as the steadily increasing length of night during autumn. As days grow shorter, and nights grow longer and cooler, biochemical processes in the leaf begin to start the color change. So it is a combination of the length of daylight and cooler weather that leads to the change. It will be a while before we see that change here in Michigan the change starts in the UP and works it way towards our area. On average the best time for color in Michigan is from late September in the western UP to late October in southern Michigan.
On a side note. There has been not only a thunderstorm drought in parts of Michigan there has also been a tornado drought as well. So far this year there have been only two reported tornadoes in the state of Michigan (the EF3 storm in Gaylord on May 20th and a small EF0 south of Flint)
Slim
What a stretch of normal to below normal temps and next week is more of the same! Incredible summer and no heat waves!
Yep…probably the best “weather event” of the year. Fourty mph gusts, and a 1/2 inch of rain in 20 minutes.
Sounds great.
Wow how the temperature has dropped in the rain definitely feels great … INDY
Quite the decent storm here. Seems at least 45-50mph winds, it’s hard to tell exactly
Getting pretty constant thunder at my house. Can see the rain and dark clouds just to my west. Getting a nice cool breeze
Turned out to be a great day. Just pressure washed the back deck. Got some serious sun. Feels warmer than 82.
Days are getting shorter … INDY
Thanks Slim. Why do the wild cherry trees start to lose their leaves earlier than the rest? Oir cherries are already starting to shed some.
This may be the cause.
“Cherry yellows is a viral disease that also causes tart cherries to drop their leaves. This classic, leaf-yellowing disease is caused by the prune dwarf virus. Defoliation is happening now and often occurs in waves throughout the season.”
Slim
Interesting…thanks!!!
They are cherry trees..but they are the tiny ones that just birds eat.
6 years since this event
https://www.weather.gov/grr/summary20160820
Hopefully we don’t see that again!
Interesting post, thanks Slim!
I can’t wait to head to the UP in only a little over a month for the fall colors.
The official H/L yesterday at Grand Rapids was 83/58 the mean for the day had a departure of 0. A trace of rain fall was reported at GRR (here at my house there was no rain fall) and the sun was out 61% of the time. The overnight low here in MBY this morning has been 67. The official low so far at GRR is a cooler 63. I am a little closer to Lake Michigan where the overnight low at Muskegon has been 69 and Holland were the low so far has been 67 at the current time it… Read more »
Thanks for the science lesson, Slim. I should make my kid read it.
Warm days, cool nights and ample soil moisture? The colors should be kicking around here this year.
Have a great weekend all.