Our recent heat wave has finally broken. Today's high was 82°, and it's already dropped a few degrees since then as a brisk on-shore breeze has picked up. This is a welcome change from recent days, the last eight of which all topped out at 95° or above. Five days topped 100°, with a peak of 106.7° on June 30th. Although the heat here at Tablas Creek wasn't quite as bad as many forecasters predicted (or as bad as some other regions further inland and north of us) it's still an extended stretch of hot weather, with unusually warm nights as well as very hot days. The below graph shows our high, low, and average temperatures over the last ten days:
Given that the next week or so shows moderate summer weather with days topping out in the 80's and lower 90's, I decided to take a walk around the vineyard to assess what impact, if any, we saw from the hot spell. While there was some damage from sunburn on heat-sensitive and canopy-light varieties like Mourvedre, I was pleased to see that the losses weren't even as bad as what we saw from a similar heat wave last August.
First, a few photos that will show you what sunburn looks like. The clusters below are typical, with berries that are on the outside top shoulder of the cluster turning to hard, dry, sour raisins while the majority of the cluster remains unaffected:
A close-up of a different sunburned cluster, taken from above in a head-trained block, shows again the typical scarring that the extreme heat leaves on the plant's exposed tissues:
These raisins will dry up and fall off later in the summer and won't impact the quality of the remaining berries in any way. But before you think that every cluster was affected, it's worth noting that at least as many clusters look like the one below after having received sufficient shelter from their canopy of leaves:
From my walk, I'd estimate that we lost between 10% and 20% of our Mourvedre to sunburn, and something much less than 5% of our other varieties. That's not negligible (we probably lost something like a dozen tons of Mourvedre, or enough to make about 700 more cases of wine) but it could have been much worse, and likely would have been worse had the temperatures gotten up around 110 over three or four days, as they were originally forecast to do.
The vineyard itself looks terrific. Hot spells like this one can cause whole blocks to start looking tired, leaves starting to yellow or brown and vines just looking exhausted. I didn't see anything like this; the canopies are almost electric green still and look vibrantly healthy. The below photo looks over a head-trained Tannat block up to Grenache Blanc on the hill:
There is still a long way to go; we haven't even seen the beginnings of veraison yet in early varieties like Syrah and Viognier. But we seem to have weathered this particular challenge in good shape, and the vineyard looks strong as we approach the midpoint of the ripening cycle and get ready to turn for home.