Impact of weather during harvest?

For the past three weeks, we've had 80% rainy days, usually cold rainy days, and even the dry ones have been overcast so that nothing dries out. Lovely today, but I'm wondering about the effect of that kind of weather on grapes for white wine.
The reason: I was half listening to the nightly news last night and there was a brief segment on the bad luck of wine growers in SW Michigan this year, with charts showing the temp and rain comparison to prior years, and then some person (I missed his name, and his affiliation) was shown saying that he was looking forward to exceptional white wine this year because "white wine loves the cold weather." But what about the rainy cold weather?

Hi OW,
You have to worry about mold and rot.

Salute

""white wine loves the cold weather." But what about the rainy cold weather"

Ow, a fool and his $$ are soon parted, this guy oprobably doesn't even need a lawyer to part him from it.

I wouldn't think that clouds and rain would be good for either reds or whites at this time of year. Being colder than usual seems to me much less important than the lack of sunshine.

Too much rain immediately before harvest can swell the berries with water, in some cases causing berries to split. This additional water can dilute both the sugar and acid. Sometimes, depending on how they are ripening, this can be a good thing. The split berries are a bad thing, as they not only invite rot, but attract bees and other insects.

I was pretty sure the rotten weather we have had would be lousy for all wine grapes because of diluted flavor, late ripening, split skins, rot and whatever, but the newscast tried so hard to separate the problem by grape color, I wondered if I had missed something. Apparently not.

Bob, I resemble that remark.

O.L.W. (Old Lawyer Willy)

OW, I have some direct experience with this problem in that the very disappointing September we had affected my winemaking plans this year quite severely. I was planning to do a dry Concord as in 2002 and the early part of summer seemed quite promising for a good-quality crop. As August drew near, though, I was surprised by the cold nights ... as September came on, however, I was appalled by the constant rain and cold, and just about the worst possible weather imaginable at the most critical time for fruit quality development.

As it stands, a local grower had some slightly overcropped but otherwise decent Cayugas (white, non-foxy hybrid grapes). I decided to pick those and make white wine from them. The wine is almost finished, but I haven't tasted it as yet.

There have been rainy vintages in Ontario in the past that surprised me with the overall quality of the whites - but I don't hold out too much hope for '06 across the board, unfortunately. I think rot must have been severe in vineyards this year. Time will tell, however.