I hate to be a pessimist but the severe drought has resulted in a lot of leaves that have already shriveled up without turning. Too wet a year can result in poor fall color, but too dry can affect it too. Farmers are starting to take in local field corn about three weeks early. But keep a close eye on fall color: it could happen early and fast so enjoy it while you can.
I'm sure we've had years when the lawns turned more brown (and it is important to remember—they did recover!) and other years I have heard more dire reporting than this year about the level of regional water supplies, but this summer has been incredibly dry for us. There will be some plant mortality from it but we won't know how much until next spring or summer.
On Fox Hill, the ridge traversed by our Deep Woods trail, spicebush has shriveled completely on the south-facing slope and bottomlands along Mine Run. But on the north side of the ridge spicebush is still green and still has the opportunity to achieve its usual clear yellow fall color. Even under the shade of an intact canopy of deciduous trees the south slope fared worse than on the north side, and the plants—even of the same species—on the normally-dry upper slopes fared better than those in the usually-moist (but now dry) bottomlands.
By the way, I guess that's where Northside Road gets its name; it is on the north side of the ridge.
On sun shadows and rain shadows
The drought has also given an opportunity to compare the location and effect of sun shadows and rain shadows. Just as a sun shadow is an area darkened by an object that blocks the sun, a rain shadow is an area (under a tree, for example) where some of the rain is intercepted by the leaves. During years of normal rainfall plenty of rain drips off the leaves, but during a dry year the area under trees can be conspicuously drier than elsewhere. Large trees also evapotranspire a lot of water and their roots draw moisture out of the soil around the tree.
The rain shadow is pretty much symmetrical around the tree, whereas the sun shadow (at least at this latitude and this late in the summer) is a circle shifted to the north side of the tree.
This year I placed an umbrella in the garden to shade Owen's sandbox. Grass that was in the rain shadow and the sun shadow still thrived, as did that that is under only the sun shadow. But grass that was under the rain shadow but not the sun shadow absolutely fried, suffering significantly worse than grass that was under neither.
We pay attention to sun and rain shadows (not to mention slope aspect and how wet an area normally is) because they affect the cultural conditions for plants growing on a site. These factors of microclimate determine what species we choose to plant where. Of course during a season like this the unusual conditions change the rules and plants that can be placed under a lot of stress.
