By Joe Joyce, WBZ-TV Meteorologist

BOSTON (CBS) – We have all been enjoying this recent taste of Fall. Signs of the changing season are slowly beginning show all around us. Some of us may already planning a leaf peeping trip and may be wondering what to expect.

Richard Primack, a professor of Biology at Boston University, says this year should be quite a bit different from last year’s disappointing and muted foliage season.

“We are certainly going to have a better year than last year. Last year we had an extremely mild Autumn; very mild temperatures; no cold night,” he said. “As a result we did not have any color change until the end of October; until the beginning of November.”

And let us not forget the historic early season snowstorm in late October 2011 which brought down leaves, and put a quick end to the foliage season.

Every year nature follows this predictable pattern with the changing colors starting north and pushing south into October; the peak color briefly lasting between 1 and 2 weeks.

“The leaves are always going to change color eventually. The question is when will they change color and how long will that color be on the trees for.”

Every Fall foliage season is just a little bit different. It is actually a very fine balance of weather conditions that determines the type of fall foliage season we are going to see.

In the summer, you want it to be warm but not too hot. You want to have adequate rainfall; but too much rain can promote fungus and disease. If it is too dry, drought conditions can impact the leaf size and health of the trees. In the Fall, we want warm, dry conditions. But the trigger to it all consists of these developing long cool nights with shorter days.

“When the temperatures get cooler, the chlorophyll, which gives the leaves their green color, starts breaking down in the leaves. This allows the underlying yellow and orange pigments that are always present in the leaves to become exposed. It takes several weeks of these cold nights for the color change to occur,” explains Primack.

At the Arnold Arboretum, there are thousands of different plants and trees which are exposed and react differently to these inevitiable changes of the season.

Michael Dosmann is the curator of the living collection at the Arboretum. He says despite the warm and dry winter and spring which produced brief drought conditions, the trees received enough rainfall this summer for the trees to have a good canopy to produce good color.

“I am pretty optimistic we will have good fall color ahead of us because we have healthy leaves, healthy trees going into the autumn, and we seem to have the right climate so far,” Dosmann said. “We have bright sunny days and just enough moisture in the soil. I think we will have another quintessential New England autumn.”

It is important to note, this favorable foliage forecast will only last as long as the New England weather cooperates. Any prolonged period period of wet, windy, snowy or warmer than usual weather could have an impact on the fall color.


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