Seems to be a wide range of tolerance... I've had persimmon damaged even under a sheet at around 27, but one of my apple trees goes through the mid 20's while in bloom nearly every year that it has a crop. I'm keeping my finger's crossed about last night's 21 at post bloom though.

If it gets down too low, I hope all the factors (cloud cover, humidity, wind) are in your favor.
Good luck.

native:

I've found apples fairly freeze sensitive during and after bloom. But like you say they usually have some crop. 21 after bloom will be a real test.

I'm thinking persimmon falls in the class with pecan, grape, and fig that not only lose fruit but also foliage in even a light freeze. But my Eureka is normally so late that it doesn't get bothered by spring freezes. We are just having a very unusual year.

Let warm water run into roots overnight if you are scared.

I've never had a frost when my persimmons were that far advanced, but on occasion I have noticed early leaf damage to kakis after exposure to temps just below freezing. I did not have any damage to blossoms or the later developing fruit in those years. Last year I did have extensive leaf damage and loss of entire crop of Rosseyanka hybrid persimmons after exposure to a very light late frost. Incidentally, this frost caused no damage to my kakis.

For me, freeze damage is a threat every spring. I know pretty much nothing about persimmons, but I do know grapes are extremely sensitive to cold once they have started to grow. I've seen plenty of damaged grapes here. At my place, any time the air temp drops below 40 there is danger of frost (I've seen frost when the lowest temp registered on my thermo was 39 degrees). If they get frost on the new leaves they are gone. Sometimes the shoot is fine if the leaves get zapped, but sometimes the whole shoot dies. Often they will push secondary buds after a week or two, but they are not as fruitful. Luckily spring is usually slow to warm around here and that keeps them from budding too early (mine are still just at the bud swell stage right now). Also late pruning can delay bud break.

Grapes are the only thing I've suffered much damage on so far. My other fruits are not nearly as sensitive. I got 26 degrees last year when my peaches were in full bloom and still had a good crop. I got worried because the flower petals appeared to be damaged. Sweet cherries managed the 26 degree event as well. They were maybe a few days further along than my peaches when the freeze hit. Apples seem to flower late enough to miss the hard freezes. I know apricots are more sensitive, but I don't even try to grow them here.

About 31F last night. Saved the tasseling sweetcorn by running a high volume of well water thorough a sprinkler. There was ice on the edge of the sprinkler pattern but not on the plants. The persimmon was covered with a tarp and a 1500 watt heater inside. It's fine. Hope this is it for freezes this spring.

Thanks for everyone's help!