i found the following expnation and "viewing" details on this site:
http://scifun.chem.wisc.edu/chemweek/fallcolr/fallcolr.html"Dry weather, by increasing sugar concentration in sap, also increases the amount of anthocyanin. So the brightest autumn colors are produced when dry, sunny days are followed by cool, dry nights.
In recent years, autumn colors have been attracting more and more tourists and travelers to prime color regions: New England, Michigan, and Wisconsin. (In Wisconsin, the fall-color tourists spend over $1 billion.) The right combination of tree species and likely weather conditions produce the most spectacular displays in these regions. States in these regions maintain a fall foliage "hotline," keeping color watchers apprised of the peak viewing locations and times. In Wisconsin, this information is provided by the Division of Tourism at (800) 432-8747 and on the Web at
www.travelwisconsin.com/search/FallColorReport.html. The U.S. Forest Service also operates a Fall Foliage Hotline at (800) 354-4595. A detailed report can be found on the Web at
www.fs.fed.us/news/fallcolors/."
A few years ago we all gor very excited over in much of western Europe when, for once, we had a hot dry summer. The autumn colours were magnificent and all the newspapers were full of explanations about sunshine and lack of rain and sugar in leaves and so on. We'd hardly thought of trees' chemical proccesses much before (or since). Ah, well. How much is an air ticket to the US?
