I came across this Penn State article.
https://extension.psu.edu/fruit-harvest-handling-of-frozen-apples.
Look like exposing apples to 28 F temp for 4 hours will result in freeze damage.
We have a prediction of low at 23 F on Fri and 28 F on Sat. I still have two apple trees full of Gold Rush and Fuji apples. I think I will play It safe and pick those apples before Fri.
Norhtern growers: Do you still have fruit on your trees when temp in your area is going to be below freezing?
It depends on the apple for me. Arkansas black can take some freezing temps.
Agree that very dense apples like Arkansas Black probably can handle it. It looks like the denser the flesh, the more ability it has to withstand the freeze.
I am quite sure my Gold Rush could handle freeze better than my Fuji. But at 23 F, I definitely do not want to risk it. I wait all year for these apples. No way, I would want to lose it to freeze.
I wouldn’t leave apples on the tree if below 25 or so. If 23 you could still process them in the next couple of days but don’t think they will be usable for long term storage
I wouldn’t risk 23 degrees even with Arkansas Black. I would pick them the day before.
I’d pick them but leave a couple on the tree just to see what happens. 
Whole night yesterday I was thinking what to do with a couple buckets of Gold Rush still hanging on the tree. Actually, not a single undamaged apple dropped so far, so they could use another 2-3 weeks on the tree, but, oh, well… I ordered 120 quart cooler that is claimed to hold ice for 5 days under 90 degrees. My plan is to put it in my shed and fill with apples and remote thermometer. The upcoming freeze is short so they should be fine. If anything, they may suffer from too warm temperature as it gets back to 50 after the freeze. If enough space left in the cooler I can add ice packs, may be…
It may more depend on how concentrated acid/sugar in the juice. Sweet and acid water freeze under lower temperature
I have a fairly arbitrary cutoff point of 28 F for nearly ripe apples if it’s not expected to be cold too long, as it also depends on duration: half an hour at 26 F might be tolerable while two hours at 26 F might be damaging, just for example. I don’t have any actual data.
The forecast moves low temp up to 26. I will wait and see if it will change in my favor. But as we know, weather forecast can be totally wrong and we get a foot of snow.
I wouldn’t risk full tree of apples. It is always gets colder than forecast in my location. I just got an idea. My apple tree is espaliered and whole tree is covered with a net. I have a big tarp. I will place it over the net on the frame and put a heating lamp inside for the night. after 2 freezing nights it should be another 2 weeks above the freezing mark. I think I can buy those two weeks!
My guess is that article is a bit conservative - if you are a commercial grower you are justifiably risk-adverse since your livelihood depends on it. I have not had any noticeable problems at 26F. 22F is the first point where I noticed problems. It also depends on the brix of the fruit, if the brix is high you will have a couple more degrees of protection.
Maybe pick most, and leave a few to see what happens to them?
When I had a red delicious tree, I would let it have a frost before we picked them, substantially improved them!
My experience strongly contradicts the article. 28 degrees doesn’t seem to affect the firmness of the late apples I grow- Pink Lady, Goldrush, Braebern, and Granny Smith. I see 24 as more the critical temp, but have seen Goldrush stay crisp even below that.
The article is probably not based on careful research that makes a clear correlation between sugar content and freeze resistance. I’m surprised that apparently careful research on the subject has not been done, or at least, I was not able to find it last time I searched extensively for it.
I removed all of my apple trees fruit two weeks ago. Zone 4b
I have monitored the hourly temp closely. Sat low will be 27F for 3 hours and 26 F for 2 hours consecutively. Actual temp. I do not consider the “feel like temp”.
Leaning on @scottfsmith and @alan’s experience, the apples should be fine. Hate to pick them when they are not quite ripe and knowing that next week temp will be in the 50-60 F for a stretch.
Here’s my bending Gold Rush tree now. If you enlarge the middle of the pic, you may see geen things on the tree through snow? 
Wow, you are lucky not to have experienced a power outage. Trees in leaf are very susceptible to losing branches in those conditions.
I went out to knock off snow from my apple trees. (Other trees have no fruit so no service for them).
Gold Rush is obviously not ripe. I shook the tree fairly hard. No fruit fell off except for the two that I accidentally hit.
Golden Russet, as soon as I shook the tree, 4 of 5 fruit fell off. One refused to come off so I let it be.
One Fuji fell, the rest stay on the tree.
I probably have
Whatever happens, happens.
