I have a young peach which I found germinating in my garden last Spring ( 2017). It is outside in my garden in a plant pot and has been outside all winter. It is now February and it still retains all of its leaves, and is even beginning to sprout new leaves for this year. It looks as fresh as it did last summer. It has withstood frosts and snow. Why did it not lose its leaves ?
I don't know what the low temps have been, and each cultivar will have a different temperature tolerance. Many of them will gladly keep their leaves through the cold periods if it doesn't get well below freezing. Here is an article for more information about peach trees: https://www.gardeningknowhow.com/edible/fruits/peach/peach-tree-care.htm