This morning, looking at the fog outside, I changed my plans to take my kids swimming at my parents' house and went to the zoo instead. Even now, at 1:13pm, although the fog has burned off and it's sunny, the temperature at my house in downtown Paso Robles is 73 degrees, and it's breezy. Not exactly pool weather. I'm not sure how frequent highs in the low-70's are in July in Paso Robles, but it's rare. I'm not sure I remember it ever happening, and this is my ninth summer out here. As a point of reference, the average high temperature in Paso Robles for July 25th is 94 degrees.
This has certainly been an unusual summer. We got our last rain and last frost remarkably late this year (both in May). June was sunny but cool, with most days topping out in the 70's or low 80's and nights routinely in the 40's. We didn't have our first 100 degree reading at the vineyard until about ten days ago, and the four days of 100-plus weather moderated again into the weather pattern we're in now.
Some of the consequences of these cool temperatures are felt now, and others we'll only know come harvest-time. For now, the relative lack of heat and the relative availability of moisture (by Paso Robles standards, at least) have meant that we've had to struggle against mildew this year more than in any year in our history. We're used not to having to worry about it; mildew doesn't like hot weather (it won't grow above about 100 degrees) and the lack of rainfall in the summer months means that once the topsoil dries out in May and June, there isn't enough moisture to support its growth anyway. But with the more frequent fog cover this year (about once a week, compared to perhaps once a month in a normal year) and the abundance of moisture in the ground from the 140% of normal rainfall we received last winter the conditions are better for it than usual. David Maduena, who manages our vineyard crew, noticed it in a section of Grenache a month ago, and he, Neil and Ryan have been going after it since with sulfur, copper, and the other organic products we have available to us. It's under control, but not gone, and will bear watching over the next month.
The longer-term consequences will be felt at harvest. We started the year a couple of weeks behind because of the late, cool spring, and this weather isn't allowing us to catch up. As a marker point, I wrote about veraison this week each of the last three years (posts dated July 24th, 2009, July 30th, 2008, and July 27th, 2007). Not only do we not see any veraison in the vineyard yet, I'd think we're at least a couple more weeks out. Plus, we were already expecting a later harvest because of the comparatively robust crop levels. Between those and the cool weather, locals are joking about harvesting at Thanksgiving. We don't expect that, but I also wouldn't schedule a visit in mid-September and expect to see everything in full swing.
On the positive side, the vines, for which extreme heat is as much as a stressor as drought, look great. The canopies are lush and green, and the work on vineyard nutrition we've done this year has been even more effective than we'd hoped because of the mild weather. And while the 100-plus days are a dramatic marker of the warmth of the climate, they actually don't help the vines ripen much. Above about 95 degrees, most wine grapes shut down their photosynthesis to conserve moisture. So, what we really want are more days in the upper 80's and lower 90's... just what is forecast for the next two weeks.
Overall, the vintage's weather is tracking most similarly to 2005 and 1999. The chart below (taken from the Paso Robles Wine Country Alliance's agricultural forecast) shows the growing degree days to date over the last 14 vintages. The column on the left is from the Tablas Creek weather station (the others, from left to right, are Summerwood in the Templeton Gap, J. Lohr in the Estrella River Basin, Red Hills Vineyard in Creston, and Shandon Hills Vineyard in Shandon):
It's also worth noting that the vintage, for all its coolness, is still a lot warmer than 1998, the coldest vintage on record. And even in 1998, we still got our grapes ripe, although we didn't start harvesting until October. In both 1999 and 2005, we had late harvests and long hang-times, and the wines we made have aged wonderfully. If the weather holds into November, we have a shot at another similar success.