I also think that, if the tops die they'll be done for. That late in the year would be too late for a come back I would think. However, you may be able to delay that with your heating cables if you throw a cover over the plants during cold spells, especially at night.

Jim

I am currently covering my bell peppers at night (temperature is between 35 and 45F @ night )and inside of that cover is clear and orange christmas lights (the old large ones) well they provide heat and alot of light and they are just blasting off in growth . It really works lol ...it was a tip from someone here on this forum I laughed at first and promised that I would try it and presto! almost better than sunlight and just the right amount of warmth .

I would guess that if the plants are in the ground it may not work but raised bed or planters ,I think you stand a pretty good chance of gaining "alot" more time (heating cables)but at least some more time if your plants are in the ground . It's hard to say if one could make it through the entire winter but zone 7 is quite promising unless very tender warm tropical plants are involved .

Well, I've read that chard will grow back from the roots the following year anyway since it has a beet like bulb. Hopefully that at least will survive the winter in my pots to leaf out in spring.

kale chard and snap peas are very hardy plants I believe they tolerate frost ....how much frost could there be in a 7 zoning I'm not sure but I think you are safe .