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Perfect weather this month helping set the stage for great fall color

Posted by David Epstein  August 19, 2013 09:00 AM

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A tremendous stretch of weather in New England continues this week with abundant sunshine, warm to hot temperatures and increasing levels of humidity heading towards the close of the work week.I'll be updating the details of the weather and telling you were to find the best fall color on Twitter at @growingwisdom Please follow me there. Feel free to comment or ask questions too.


Yesterday ended up cloudy and was even wet for Cape Cod. The reason for the not so beachy day was a stalled front off our coast. The front was the conduit for clouds and showers to stream northward along its boundary. The front is now further away and so our clouds have thinned.

We will still see some high clouds today, but not to nearly the extent of Sunday. Temperatures will be warm and humidity levels low. I like days like today for heading to the beach because they are not blazing hot.

Temperatures will increase a few more degrees Tuesday, Wednesday and Thursday with highs getting into the upper 80s and lower 90s. A sea breeze can keep coastal locations cooler after 2 PM. Remember, weather can be highly variable even within a coastal town so use these numbers as a general guide.

We have not seen any ninety degree weather this month. I do think that Boston could officially hit 90 both Wednesday and Thursday. It will feel hotter than 90F because we are no longer use to that kind of heat. The good news, if you don’t like the heat, is it will dry out and cool off for the weekend. Highs over the weekend will be in the 76-80F range with sunshine.

Fall Foliage Preview

All this dry weather is going to start to cause minor issues with lawns and some other plants which might need more regular rains. However, it has been such a wet summer, a major drought is unlikely.

The cool nights and warm days of the past couple of weeks may have been a contributing factor in bringing some early color to a few trees. Generally, trees and shrubs that show color in early to mid-August are under some sort of stress from disease, heat or insects that brings on the change in color.

Remember, the purpose of the leaves on plants is to make food (simple sugars) for the plant to survive the winter and then leaf out again next spring. The transfer of food from the leaves to the branches and roots of a tree takes place from the time they leaf out in spring until sometime in late summer and early fall. Additionally, the roots are taking up nutrients from the ground and sending it to the leaves to make chlorophyll. Chlorophyll needs to be constantly replaced during the spring and summer to keep making more food to get that shade tree through the fall. It's a great process.

Over the next few weeks a layer of cells, called the abscission layer, will rapidly grow and basically damn the flow of sugars from the leaves to the rest of the tree. You probably were taught the fall color of the leaves comes from them dying, but part of the process starts with rapid growth, not dying, of that new layer. This same layer works both ways and blocks the flow of nutrients from the tree into the leaves. As this happens, thegreen pigment, the chlorophyll, can no longer be manufactured. Without the Chlorophyll the yellow pigments known as xanthophylls and the orange pigments called carotenoids — both then become visible when the green chlorophyll is gone. These colors are present in the leaf throughout the growing season.

This is different than the red and purple pigments which come from anthocyanins. In the fall anthocyanins are actually manufactured from the sugars trapped in the leaf. In most plants anthocyanins are typically not present during the growing season.

The best weather for great color for September and October will be generally dry, but not too dry. A wet second half of August and September will not be good for fall color. We also need to have cool nights, but not frosty nights for optimum color this fall. So far, we are on track for a great season ahead, but of course it could all come crashing down with one big early season storm.
Gardening this week
Tomato and corn season is upon us here in New England and the produce is wonderful. My own tomatoes are now coming to maturity and the video below is an update to one tomato plant I rescued last fall from a sidewalk at Framingham State. The plant was growing in the crack of the concrete and I kept it alive all winter.

I'll be updating the details of the weather on Twitter at @growingwisdom Please follow me there. Feel free to comment or ask questions too.

This blog is not written or edited by Boston.com or the Boston Globe.
The author is solely responsible for the content.

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About the author

David Epstein has been a professional meteorologist and horticulturalist for three decades. David spent 16 years at WCVB in Boston and currently freelances for WGME in Portland, ME. In 2006, More »
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