Willamette Valley heat

For those who might wonder why the Willamette Valley is a special place for grape growing, the current weather is a perfect example.

While we are currently seeing some very warm day time temperatures, 99F yesterday, 100 today and 103 tomorrow (in McMinnville), the corresponding night time lows are 59 F, 61 and 58. The day after that the predicted low temperature is 51 F (88 F for the high and it’s mostly high 80s for a while after that).

For all that the news media is having a field day with the warm weather, and I feel for anyone who has to be outside in the heat of the day, this is really only a few degrees above normal summer heat for us. It’s a bit earlier in it’s arrival than usual, but the diurnal shift is about 40 degrees. The plants definitely get a respite from the heat and working in the early morning is quite cool. First light is about 5:00am and vineyard work wraps up by noon.

It’s definitely hot weather but the cool nights will keep us in balance.


Elevation is everything. Ww’re about 500’ above sea level, and we’re seeing higher lows but also lower highs. We haven’t broken 96 yet, but nights get down to only about 70.


That’s interesting, especially as Whistling Ridge is about 500’ in elevation, along with our Pinot Noir Block at Durant.

Temps at the vineyard we’re about 97 yesterday and the 4th, but the wind was blowing by 5:00pm and nights were below 60. The corridors letting marine winds in from the coast are a huge factor in growing grapes here.


So given that this heat is only somewhat hotter than usual, the timing of this heat, and the magnitude of the daily diurnal, is there anything we can glean about how this weather might be affecting the fruit? Or is it too early to say?


It’s pretty early to have aany hard and fast ifeas about how it will affect the fruit.

As each weather event stacks up, a lot depends upon the preceding events. We had a wet but mild winter, so good soil moisture but an early budbreak. Then cold weather after that, not cold enough for damage of any kind but definitely cold enough to delay bloom. We had a pretty balanced set at Whistling Ridge, good sized clusters but not every berry set. So good spacing on clusters and a decent but not heavy fruit set.

My guess is that Whistling Ridge will handle this heat, especially with the cool night temps. It will advance the fruit a bit but we’re nowhere bear versison. And often when it’s above 95 the plants kind of shut down, I suspect this year that’s less likely due to there being reasonable soil moisture. Though like any buffer, the soil moisture will take a hit from this. Especially in faster draining sedimentary soils. So hopefully we have a nice moderate rest of the growing season.


Same phenomenon is what has always fascinated me in Anderson Valley, especially as you get to Philo and points west. There are often heat waves but night time temps are always in the 50s. Also means in takes until noon to really heat up much and the cool winds start blowing early afternoon. By sunset/dinner it’s always jacket weather again!

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I would think corridors are a major factor, certainly true down here. Are there local variations depending on degree (so to speak) of influence from the corridors?


That’s very similar to the Willamette Valley.

And to asnwer Al’s question as well, there is definitely some differentiation in micro-climate due to the corridors, but overall temperature shifts affect the entire northern part of the Valley (that’s not to exclude the Southern half but I have no experience there so I’ll keep it a comment about where we source fruit from).

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Thank you, I didn’t know Willamette had that level of diurnal range. I love bringing up my weather app and, when it’s 99-83 and humid here in North Texas, Paso Robles is 103-58. It’s nice to dream of being there.

Yes, Paso Robles is one mountain range from the ocean (25-30 miles, or so) with a very substantial afternoon breeze blowing through the so-called Templeton Gap (46W basically goes through the gap) that has a significant cooling effect.


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In Indepence, OR now. Onto Eola-Amity Hills tomorow. Hot enough.

Crawford Beck Vineyard in the Eola Amity Hills (387-521ft elevation) has a public-facing weather station (only one I know of). The temp graph really highlights the diurnal shifts that you mention, Marcus (picture below) – we just don’t see too many hours at 90F+ per day and the vines are booming. (Unfortunately we can only see the last ten days on the site – I didn’t get to this soon enough to capture the 4th, etc). The link to their weather station can be found here.

In related news, Results Partners presented information at the recent Eola Amity Hills AVA meeting (they mange dozens of vineyards throughout the northern Willamette Valley and beyond): cluster counts are coming in high this year at 2.0 ave/per shoot across sampled vineyards in the northern WV (obviously can vary site to site). The norm is 1.7

Vitis Terra also presented and Jessica noted that many vineyards have shatter (coulure) similar to what you are seeing, Marcus.

Image 7-15-24 at 1.40 PM

That graph is a great way to see the shifts David, thank you for posting it.

97 (or more) today. 59 tonight.

As much as the Paso crowd like to tout this feature, I find the claims to be a bit overblown. Paso is pretty damn hot, and that one mountain range is substantially more of an obstacle to the cooling impact of the ocean than, say, the coastal range in the southern half of Sonoma County. The cooling off at night is much more due to the low humidity than to the ocean effect. The Templeton Gap is much less of a gap than the Petaluma Gap. A few weeks ago I was driving back north from the Santa María Valley. As I left SLO at 4pm and started the ascent across the coastal range, it was 78 degrees. About 10 minutes later as I got over the range it was 101. Driving up valley, I reached Templeton ten minutes later, where it was…97.

Diurnal shift looks pretty similar. I think the difference is that the effect of the Templeton gap varies much more across the sub-appellations around Paso. SLO, btw, is very cool because it’s essentially coastal, not inland.

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Fair to say - certainly the western area closer to the gap gets more impact. Maybe I’m spoiled by my generally cool evenings here in Santa Rosa, I’ve just spent too many sweltering nights in Paso, wishing the Templeton Gap was a more efficient cooling engine.

yesterday I had to go to the DMV in Hillsboro. around 3pm my car read 95 when I left. drove home, a much higher elevation than Hillsboro and the car read 88. I am pretty high up in the Willamette Valley, pretty much at the peak of Bald Peak so I have been experiencing the swings, but not as wide a range. during the day, its about on average 5 degrees + cooler, but at night it does not cool down as much or as fast as the valley floor. My observations are limited as I have only been in my new house for about 1 month. But the weather does remind me of the bay area with the nice drops in temps when the sun goes down. the only difference I have found is that it is slightly higher in humidity here in OR and when the sun goes down, the breeze kicks in and helps things feel cooler. I was sitting on my deck last night around 9pm, temps read 73 nice breeze and it felt almost chilly. Looking at the 10 day forecasts, every day shows the 30+ degree split in the highs and lows. when I drive by vineyards, they all look nice and healthy!


90 yesterday at the height of the warmth and 55 at 5:00 this morning at the winery.

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PWS Monitor is a downloadable app that allows you to see a large number of networked weather stations almost anywhere in the US (I haven’t tried it for outside the US). Many of them are home weather stations that aren’t necessarily calibrated or placed correctly but they are still a pretty good indication if you can look at multiple stations over time in a given area for consistency. They are pretty good for temperature and humidity. Wind and precipitation totals would be the least reliably accurate readings due to placement considerations.