I'm with you. I think they would cook under the solar heat, especially the ones under the black bags. The 55 degree daytime temp certainly is not going to harm them. Why risk cooking them?

You are getting frost warnings earlier than we are here in central and southern MN. I'd better start keeping my ears open though. I often miss the warnings and it puts a finish to my garden. The peppers seem especially vulnerable. Carmellia

I use old sheets - they work great, and if you are a little late uncovering them they don't cook so badly underneath.

-Marie

It may be too late for this year but here is something I have done. Check thrift stores for half off tags, church rummage sales for bag days etc. You can find a lot of discarded material, large king size sheets, or other fabrics that are not very expensive. I have even gotten tarps from the box stores for $1-$3 after rebates that I use to cover things.

Good luck and keep the frost over your way for awhile yet.

Thanks all. Sorry I didn't respond earlier, but GW has a nasty tendency to freeze up my home computer. Anyway, just to let you know - the lowest we got was 32.5, even my uncovered basil survived! So the covering probably wasn't necessary, but I would have been bummed if I hadn't covered and they had frozen. The day I asked about - the issue was not worrying about the daytime temp, the issue was the amount of time it took to cover all the plants and the fact that I had to be somewhere that evening. I kept an eye on the plants during the day - stuck my hand up in there and it was warm, but never hot. I think if it had been a really sunny day it would have been a problem but, because it was cloudy I left them covered and they did fine. So, now we know for the future.

I thought about using sheets also, but the plants are spread over a very large area, so it would have taken a lot of sheets. I'm not sure I could have fit more than one tomato under each sheet! But, as deweymn suggests, I will try to find very inexpensive ones and collect them for the future.

Thanks for the comments
Ann

I say, take advantage of all the sunshine you can right now. You'd be sorely dissapointed if you lost your plants to overheating rather than to freezing, but that's just my opinion.

I cover my plants with a variety of old sheets and that filmy white row cover. Over the years I have often left the plants covered until early afternoon as I am often up all night and therefore sleep during the morning hours. Sometimes I have even left plants covered all day if there is frost expected again that night. I have never had any of my plants damaged from heat resulting in being covered. I expect that is more likely to happen with plastic and tarp coverings.

That said, it's a lot of work to cover and uncover plants so unless it is very early in the season, like this past week, I only cover a few very select plants. It is actually a relief to have the season end.
Bobbie