Last year was my first year, so this is a relative newbie answer. Just fair warning.

I only had a few jugs, but I did open them when temps were high and sunny, so they didnt fry, but then if it was going to be colder than 40 at night I had to run back out and recover them so they didnt freeze at night.

As for sunburnt, my experience is that very new seedlings, especially ones without yet a true set of leaves, are still sort of blank slates. You can put them out in full sun and they just adapt. But if you've had something that has been growing to six inches and several sets of true leaves, but has mostly been overcast (or inside), then that plant may get sunburnt.

But I havent ever had any WS seedlings get sunburnt. It seems to be one of the advantages of the WS method. And I havent particularly heard of people opening up containers in stages, similar to the way people have to baby insider plants along an hour at a time.

Though you could probably hedge your bets if you are nervous and open half of them.

Thank you emcd124! We are supposed to stay 48 or over at night for the next ten days, so at this point I am less worried about frost.

And since I have CLEARLY over done it on sowing maybe it would be a blessing in disguise if I end up frying some of them! I think I'm going to be brave and take a great deal of tops off.

I have been WS'ing for several years.
All of my containers are against a brick wall, facing south/east - so the hottest place they could be.
I take the lids off once the temps reach the 50's and leave them off, altho I cover them if it goes back to the upper 30's.
I've never had anything burn. Perhaps there are things that would, but nothing I've sowed ever has.

Thank you ellenrr!

I cut my tops off! I'll keep an eye out for the temp going below 40. The next few weeks look fine so far.

My next project is to try and get stuff raised up so the rabbits don't think it is a buffet!