Don't trust your own senses, in determining whether this is a hot summer!

Here's what I just wrote to my fellow grapegrowers in SW WA (and, first, you need to know that Growing Degree Days measure heat which is a proxy for sunshine; growers use GDDs to know how warm their growing season really is):

It's been so hot for the past few days that it seems strange to get this result, but we had a late, cool Spring, and:

I know the high-lo temps for today and tomorrow, so I can calculate GDDs (F; base 50) for Jan 1, 2020 through July 31, 2020, and the total is: 1189. That is the lowest of THE PAST SEVEN YEARS.

Next, I took the 15-day forecast and used that to project all of August, and that adds 604 GDDs, for an Aug 31 total of 1793 (but if the 2nd half of August is cooler than the first half, which is normal for us to see, that 1794 estimate will end up being a bit too high). That is the lowest of the past 3 years (but not the lowest of the past 7 years).

In recent years, September has added about 500 more GDDs (it varies a lot depending whether the rains come early--last year, Sept only added 250 GDDs). So if we get "normal rain return date" (about Sept 21), that might leave us at about 2290 GDDs by Sept 30. That is better than average for this area, if you look at the past 50 years, but due to recent climate change it would also be the second-lowest of the past 7 years.

So I am going to continue dropping fruit now, to help the remainder get fully ripe, just like last year, on all my varieties except the ones that have shown they can ripen a huge load no matter the weather (only some of my modern varieties can do that). If growers let a full crop hang, I predict they may have less-ripe flavors. It's a very difficult decision to make, of course, as each grower has to think about their own fruit quality and income needs. 

Comments welcome,

Kenton

Your Education Committee Chair