Yes, July really was hot. But veraison still arrived late. What gives?

A month ago, I felt like I was tempting fate when I characterized the 2018 summer as "benign". Well, so much for benign. July was the hottest month we've ever seen here at Tablas Creek, with an average high temperature of 96.5 and an average overall temperature of 76.5.  Fourteen days topped 100, and only seven -- all toward the beginning of the month -- failed to get into the 90s. In terms of degree days, July saw us accumulate 844 degree days, fully 28% more than our average of 659. That's a big increase over what is already our hottest month:

Given the heat and the season, it really wasn't a surprise when I got an email from Neil on Monday with a photo of Syrah undergoing veraison. Veraison marks the point where a grape stops accumulating mass and starts accumulating sugar. More visibly, red grapes start their color change from green to purple, while white grapes take on more of a yellow tint. Both red and white grapes start to soften. [For more about what's happening chemically, check out this veraison post from the archives.] A few photos of Syrah clusters will give you a sense of what things look like now:

And:

It's worth remembering that most of the vineyard is still totally green.  Syrah is the first red grape to enter veraison, and I couldn't find even a hint of color on any of the others. And, that photo was from the top of our tallest hill, which is always more advanced than areas lower down both because they started earlier since their last frost was later, and because they're under more stress due to scarcity of water. But we know that once we see Syrah, the other grapes follow along in fairly short order.

One of veraison's principal values to a winery is as a marker: this landmark comes roughly six weeks before the onset of harvest, and gives us our best estimate for when harvest will begin.  But, of course, six weeks is a rough average, and can be influenced by the weather that we get in the interim, as well as by the amount of fruit the vines are carrying.  For example, in 2014 our earliest-ever veraison (noted on July 9th) was mitigated by a very cool August, and we started harvest 45 days later, on August 23rd. By contrast, 2016's first veraison was noted on July 13th, and combined with a very warm August to produce our earliest-ever beginning to harvest, just 36 days later. The last dozen years are compiled in the chart below, with each year linked to my blog post about that year's veraison:

Year	First Veraison Noted	Harvest Begins	# of Days
2007	July 20	August 28	39
2008	July 23	September 3	42
2009	July 20	September 1	43
2010	July 30	September 16	49
2011	August 5	September 20	47
2012	July 25	September 5	42
2013	July 17	August 26	40
2014	July 9	August 23	45
2015	July 18	August 26	39
2016	July 13	August 18	36
2017	July 20	August 30	40
2018	July 29	?	?

Using the range of durations between first veraison and first harvest (36 to 49 days) we can have good confidence that we'll begin picking sometime between September 3rd and September 16th. I'm guessing we start toward the early end of that range, given the warmth of the summer so far and the relatively moderate crop levels we've been estimating.

Given the heat in July, it's worth addressing why the vineyard hasn't caught up more from the roughly two weeks late it was after flowering. I'd point the finger at two culprits. First, we did catch up a bit; I'd estimate that we're more like 10 days behind than the two weeks we were in early July.  And second, grapevines photosynthesize optimally at temperatures between 30 and 35 Celsius (86 and 95 Fahrenheit). Two-thirds of our days in July got above 95 degrees, which means that the grapevines actually slowed down photosynthesis in the heat of the day as they closed the pores on their leaves to reduce dehydration.

What's next for the vineyard? We'll watch the different grapes go through veraison. Syrah will be followed by Mourvedre, then Grenache soon, and finally Counoise. In the cellar, we'll be getting the last of the year's bottling done so there's space in barrels and tanks for the coming crush, and starting the process of pulling out and cleaning all the tanks, barrels, and equipment we'll be using once harvest begins. Everyone will be storing up on sleep.

And now we know -- roughly at least -- how much time we have  left before everything shifts into harvest mode. Stay tuned.