Just how hot has the summer of 2016 been? More (and less) than you probably think.

I woke to a chilly morning in Paso Robles today, under an overcast sky that seemed equally composed of smoke and fog. The low this morning dropped into the upper 40s, and when I got to the vineyard it was still in the low 60s.  This is a change from the last two weeks, which have been very warm, with an average high of 98.2°, an average low of 57.2°, and six days that topped out over 100°F.

I was interested to research just how warm July was, compared to normal, and I was a little surprised that while it was on the warm side of average, it wasn't as warm, comparatively, as June.  Looking at growing degree days (a commonly used heat summation measure that accounts for both how much time is spent above a baseline temperature (typically 50°) and how much the temperature exceeds that baseline) we saw 689 degree days in June, about 10% above our 20-year average of 626.  The data is probably easier to make sense of in chart form:

As you can see, in a typical year, the heat peaks in July and August, with June and September still quite warm.  This year, July was indeed hot, and June nearly as much so: 34% more heat accumulation than normal, above our average July total. Looking at the difference vs. normal shows that dramatically:

What pushed June's degree days to such high levels? Two stretches of sustained heat, at the beginning and end of the month, were wrapped around a more moderate middle of the month. The beginning of June saw an eight day period from 6/1 to 6/8 with high temperatures in the mid-to-high 90s and lows around 50°, which isn't unprecedented but is still unusual that early in the year. And then starting 6/19 we saw twelve hot days in a row, with the lowest daytime high measuring 97.1°, nine days in triple digits, and three that topped out above 105°. That's hot, at any time of year.

Late July's very warm weather was balanced out by the first half of the month, which was just about textbook average for the season: two weeks with highs each day between the mid-80s and mid-90s, and lows between the mid-40s and mid-50s.  

And about those cold nights: one thing that bodes well for the vintage is that despite the warm days, we have still had more cool nights than the past couple of years -- 25 days in June and July that dropped into the 40s, vs. just 16 last year and 22 in 2014.

The net impact of the warm close to July has been an acceleration to the veraison that we saw start in mid-July. I took advantage of the cool morning to hike through the vineyard and get a sense of where the different grapes are sitting in their path to harvest. Overall, I think we're almost exactly at veraison's midpoint, with just as many berries now pink to red as there are still green.  Of course, that varies quite a bit by variety, and even within a variety, with cooler spots at the bottoms of hills typically quite a bit behind those same grapes at the tops of the hills.  I'll take them in the order in which we saw veraison start, beginning with Syrah, which I would estimate is at 90% versaison:

Next to go into veraison was Grenache, which I would estimate is about 50% through the process. Note that it was hard for me to get out of the grenache blocks to take photos elsewhere; it's such a beautiful grape, particularly at this time of year when a single cluster can look like a rainbow:

Mourvedre isn't far behind the Grenache, though I found it a lot less even, with many vines that still had small, bright green berries on every cluster even as there were some clusters that looked like they were almost all the way through.  Overall, I'd estimate Mourvedre is at 40% veraison, and the cluster below only slightly more advanced than the average:

Finally, Counoise, which is only going through veraison at the tops of the hills, and even there there are more fully green clusters than there are those that look like the one below. Overall, I'd estimate it's only at 10% veraison:

Of course, red grapes aren't the only ones that go through veraison, but it's hard to photograph the subtle changes that white grapes undergo. Two photos might give a bit of a sense. First, Roussanne, which is our last white to ripen, and in which I couldn't find any signs of the softening or turn from green to gold that would indicate that the process has started:

Compare that to this shot of Viognier, which will likely be our first white to come in off our estate about three weeks from now:

Whether because of the cool nights, the (somewhat) better rainfall we got last winter, or the work we've been doing with biodynamics to make sure our vineyards are as healthy as possible, it seems like the vines are showing fewer symptoms of extreme stress than they were at this time either of the last two years.  And we're hopeful that we'll avoid another hot stretch at least in the near future; today's forecast is suggesting near- to below-normal temperatures over the next ten days.  If we can replicate the cool August weather we got in 2014, we'll be happy indeed.