Chill hours are a moot point in the Pacific Northwest, especially west of the Cascade Mountains, as the temperature averages are ~ 45high & 35low for several weeks. I would have guessed around 1,200 for this season to date, in line with the Bradyb posting for the Seattle area. We passed 1,000 some weeks ago, it has been warmer since.
Here are our numbers for last year:
Below 45 Model: 674 chill hours
Between 45 and 32 Model: 586 chill hours
Utah Model: 50 chill units
Positive Utah Model: 983 chill units
Dynamic Model: 17 chill portions
Contrast that with what we have so far this year:
Below 45 Model: 835 chill hours
Between 45 and 32 Model: 703 chill hours
Utah Model: 487 chill units
Positive Utah Model: 966 chill units
Dynamic Model: 30 chill portions
Not a huge difference in hours below 45 but a HUGE difference in Utah and Dynamic hours. We get plenty of cold nights here on the outskirts of Phoenix, but then can swing back up in the mid 70ās during the day. According to the newer models anything over 65 degrees counts in the negativeā¦thats what kicks our butt. Ive come to believe that they are right tho. This year we have had many cloudy cool days, thats why our Utah and Dynamic numbers are so much better.
Donāt you mean several months?
The PNW has more chilling than anywhere else in USA.
Well I myself think the calculator is extremely inaccurate Or the weather station it used for my area, as it is way off for last year. Like not even close. And looking at others who gave data from 2 stations. I donāt see how 2 miles away one would have 500 more chill hours? Something is not right there too.
These are closet to meā¦not to shabby for us. Next year I will have my own station! 
Below 45 Model: 426 chill hours
Between 45 and 32 Model: 392 chill hours
Utah Model: 466 chill units
Positive Utah Model: 747 chill units
Dynamic Model: 26 chill portions
Below 45 Model: 534 chill hours
Between 45 and 32 Model: 500 chill hours
Utah Model: 313 chill units
Positive Utah Model: 906 chill units
Dynamic Model: 27 chill portions
Below 45 Model: 208 chill hours
Between 45 and 32 Model: 208 chill hours
Utah Model: 142 chill units
Positive Utah Model: 677 chill units
Dynamic Model: 26 chill portions
Itās not the calculator problem, itās the input data problem. Some of the WUnder weather stations are rather new, for example, we have a station nearby that started three weeks ago. So, if you use data from a station that did not exist for a part of the time period, the results will be useless.
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The high-chill station is around 2300 feet in the foothills of the Santa Clara Valley. USDA classifying the location as 10a may be the source of the incongruity.
I cannot vouch for it in the least . . . .
Out of curiosity, I compared the GetChill number for a station in Gilroy near the station U.C. Davis uses for its chill accumulation reporting for Santa Clara County. The numbers were close.
U.C.Davis station @
Elevation: 185
Latitude: 37Āŗ0ā54N / 37.015026
Longitude: -121Āŗ32ā13W / -121.537040
Hours <45 = 722
Hours < 45 and > 32 = 629
GetChill Report for station KCAGILRO22 @
Elev 240 ft
Latitude: 37.03 Ā°N,
Longitude: 121.61 Ā°W
Below 45 Model: 739 chill hours
Between 45 and 32 Model: 646 chill hours
I agree with Stan, itās not the calculator itās the data. Junk in junk out. Thereās a lot of missing and inaccurate data. These are just home systems. Canāt expect good numbers on a regular basis. And even if the data is good the site may differ from yours.
If one wants good data youāll need your own station properly calibrated and maintained. Even thatās not a sure bet.
Steven is right. The reporting stations are totally privately held. They report via wifi to a router and then the data is uploaded to the weather underground site. Not all stations are functioning properly. This is why we bit the bullet and bought our own weather station and became a reporting station (KAZARIZO4). I know when mine is working and not, and crap does happen. Routers break and screw up. Batteries fail. If you arent paying attention there can be major gaps in the data.
Id encourage anyone in a low chill area to do as we did. I think it cost us just a little more than $100 to buy the station. Its located right in the middle of one of our orchards. I dont have to wonder if things are accurate.
what model did you buy?
Below 45 Model: 1505 chill hours
Between 45 and 32 Model: 908 chill hours
Utah Model: 941 chill units
Positive Utah Model: 1020 chill units
Dynamic Model: 54 chill portions
Eastern panhandle of West Virginia
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and even if data are accurate, the fact that there are several models and permutations being proposed- it goes to show the studies are mere estimations of the still mysterious science behind chilling requirements. As with other studies in biology, say-- it is still a matter of approximation when predicting the risk of getting lung cancer for someone who smoked one pack of cigarettes a day for 5 years, compared to someone who smoked half a pack/day for 10 years. We can predict there will be a positive correlation, but it is still a bit fuzzy
the only perk about such models (speaking for myself), is that could always blame weather stations for having posted dubious findingsā should my apples yield poorly, lol!
fruitnut: No, several weeks will do. Our averages on this date are already ~50/40, and at the beginning of the season, we donāt get that cold until December. Several weeks of 18-24 chill hours per day add up fast. The trick around here is to get below 45 at night anymoreā31 inches of rain since October has meant many mild nights.
Those temperatures with cloudy skies are almost perfect chilling weather. Yes 45/35 is slightly better but 50/40 is still at least 20 Utah hrs per day. Clouds help because then the sun canāt warm flower bud temperatures above air temperature. Much of the PNW, esp west of Cascades, has at least three months of very high chilling conditions. Most other areas of the country have too many hrs outside the ideal range of 48/38.
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Well with us moving into 80 degree forecasts for the next 10 days it looks like our chilling period is over. This is how we panned out for the winter 2015/16 season:
Below 45 Model: 894 chill hours
Between 45 and 32 Model: 743 chill hours
Utah Model: 506 chill units
Positive Utah Model: 1005 chill units
Dynamic Model: 32 chill portions
Its impressive to me, highest chill numbers ive seen for my location. Dynamic numbers are more than double what we saw last year. Utah hours are the most drastic change. We only accumlated 50 total Utah hours last season.
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Those are impressive totals for your area. Let us know how it affects your trees.
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At my last chill check in hereās where we wereā¦
27 DAYS AGO
Below 45 Model: 43 chill hours
Between 45 and 32 Model: 43 chill hours
Utah Model: -738 chill units
Positive Utah Model: 149 chill units
Dynamic Model: 6 chill portions
As of today weāre closing in on 200 hours and a cold snap is expected this week so we should easily pass it. My question is at what point do the chill hours stop accumulating? We went into the 70ās about a week ago, does that do anything to negate the hours?
Below 45 Model: 187 chill hours
Between 45 and 32 Model: 185 chill hours
Utah Model: -1010 chill units
Positive Utah Model: 370 chill units
Dynamic Model: 16 chill portions
My feeling is that once buds start swelling itās too late for further chilling. You are obviously in a warm winter area and normally only Nov if cold enough thru Jan can be counted on for effective chilling.
seeing bud swell on one of my pear trees and some of my blueberry bushesā¦my apple trees never completely lost their leaves this year, so Iāll be curious to see what they doā¦
PURLING NEW YORK 35 MILES SOUTH OF ALBANY A OF TODAY
Below 45 Model: 1806 chill hours
Between 45 and 32 Model: 997 chill hours
Utah Model: 1023 chill units
Positive Utah Model: 1065 chill units
Dynamic Model: 60 chill portions
MIKE