I've moved them completely up against the side of the house and they have harvest guard over them. I took a reading of the soil temperature, was about 65 degrees just now (air temp was 58). Forecast for the next week is all in the 60s but nights will be in the low 40s and high 30s. Shouldn't be any frosting.

Could you tell us where you are located? It is far too early/cool for peppers to be out except in the deep south. They end up stunted and unproductive. Recommended soil temps for peppers is a minimum of 70 degrees.

Dave

How do you use harvest guard? It doesn't provide warmth itself, it can just keep the warmth of the soil. So only way it can help you is to cover whole pot to the contact with soil bellow the pot. It will be even better, if you use old fashioned(non-led) tree lights line and wrap it around the pot and leave it on at night covered with harvest guard. Also keep in mind that many plants wilt not from the cold itself(if it is not actually full frost) , but more from a big difference between temperature ate root level and leaves level. If you leave your pot itself uncovered by the morning it takes air temperature. But as soon as sun comes up and starts warming up the air and very top level of soil, the deep inside it is still very cold. Leaves start evaporate water, but roots can't pump water up to the leaves, this is why the plant wilt. The point it, if pot got really cold, try to warm up the soil first, for example shade the leaves from sun, and cover the pot with black material.

Peppers are VERY frost intolerant. So if they were exposed to 32F or lower, they're toast. Be aware that an insulating blanket that just covers the peppers won't keep them warm. It has to be anchored to the (warmer) ground, and be sealed all the way around that anchor. That is, a piece of that (warmer) ground has to be under the blanket as well. The heat from the ground then radiates under the blanket. I have a neighbor who carefully wrapped a frost intolerant potted shrub with an insulating blanket. It got killed in a frost. Why? Because she just wrapped the shrub. Many people don't use those blankets correctly.

An insulating blanket wrapped around a person keeps the person warm. An insulating blanket wrapped around a plant doesn't keep the plant warm. That's because a person generates heat, and a plant does not.

(I finished this note without seeing what galinas wrote, which is correct.)

Agree with Galina's post but I just wanted to mention that I'm experiencing a similar, but not as drastic, wilting with my high tunnel planted peppers. We had a long spell of overcast, cold days followed by a cold but very sunny day today. I believe that under situations like that the plants need to readjust to full sun again. Shade cloth or sprinkling water on plants has helped but most often the plants recover by sundown and handle the next sunny day a little better.

Gardenviking, your experiences may be different since your plants seem extremely wilted. They might have recovered already but i believe the degree of stress and outcome would be better if you would have gradually reintroduced sun, ie,. Reharden off the plants.

Considering OP's weather forecast and likely climate, those peppers are hopeless. Get new ones in 3-4 weeks. Too early for peppers.

Yea, unfortunately it was in the 70s when I put them in the containers and the forecast was better at that point. I think it was really the wind that hurt them the most earlier in the week. 40-50 mph really whipped them around. My tomatoes and other peppers still seem to be doing better.

growing mix looks very dry.
Have you stuck a finger in it to check?

Location? Like Dave said it's too early most places for peppers, They look like their done.

I've put them inside at night and cut off the dead leaves and they're showing some progress sprouting new leaves.

I notice you're not answering where you live, so I'm guessing you've figured out that you put them outside way too early. :) Generally, you don't want to put tomatoes outside until the LOWS are consistently above 50 degrees, and peppers until the LOWS are above 55. That's typically a good couple weeks after your last frost date, unless your long range forecast says differently. Baby those damaged plants as an experiment to see how they do, but don't count on them as your main crop; you may not get much from them even if they survive. Since you say you have others in pots that are still OK, put them outside when the daytime temps are in the 70's, but bring them all inside at night until the lows are above 50-55. Peppers like it warm, warm, warm, even warmer than tomatoes. Good luck!

Not as hopeless as some suggested. :P