Chilling hours on coast

Asked December 14, 2017, 1:18 PM EST

North of coos Bay, just inland. For bare root fruit, thanks. Has there been any decrease in the last 10 years or so, that people should expect lower hours in next 10 years?

Coos County Oregon

1 Response

That's a great question!

I've been doing some work calculating chilling hours for cranberries, and happen to have some data for you. Yes, we had a REALLY warm winter in 2014-15. Based on the calculations I did using the AgriMet Crop Weather Station ( located in Bandon, during that particular winter, we had right around 1000 chilling hours. I used 45 degrees Fahrenheit as the upper threshold, and 32 degrees for the lower. The temperature sensors were located at canopy height for cranberries, which is pretty low to the ground, but I think we can look at the attached graph and see trends that would apply to your question.

When you look at the linear trendline I included with the data (the dotted red line), you can see that at this particular site, there is actually a slight increasing trend in chilling hours each year. But you can also see that there seem to be cycles in the 25+ years of data I had available. Nothing's constant, and I guess that's what makes life fun and interesting.

If you had problems with your fruit trees a few years ago, it may have been the result of a lack of chill hours. It APPEARS that we're on another upswing, but time will tell.

On another note, I was looking at crop weather data this fall (2017), and was surprised to see that many of the coastal sites I was exploring in SW Oregon were actually several weeks BEHIND normal (cooler) with regard to temperatures and growing degree days. There's definitely a microclimate component to climate, and perhaps along our coastline we are buffered against warming temps??

If you're interested in looking at weather data at your location, you can do that - or at least get really close. is a website hosted at Oregon State University that you can explore.

If I go back to your question, I don't have any concrete answers for you. If the trend we've seen over the past 25 at the Bandon weather station is any indication, it does not look like we should expect lower chilling hours in the next decade. Perhaps we'll see more drastic swings up and down? Perhaps there will be a return to colder winters? I don't know. We'll just have to wait and see. In the meantime, purchasing any new stock that has been acclimated to our mild coastal climate is always a good thing.