Are these in the ground cold-hardy plants that don't need protection just the maturing fruit?
Seed from Poncirus that go through cold winters in the SC upstate will germinate, so if the fruit are mature enough, the cold probably won't harm them.
The seed may be mature enough to germinate and grow now, even though they were set in June. I had 3 fruit from a tangerine X PT cross this summer and a fruit split open in July and another in August. The fruit ripen late October. Anyway the seed from the fruit that split in August were firm and germinated when planted. These seed were two months immature. The seed from the one remaining mature fruit are just starting to germinate.
Also I believe if you pick and store the fruit, the seed inside will continue to mature as long as the fruit is alive. Of course the fruit will start to die after a month or so but it can buy some time.