can I leave the flats (shoeboxes) of tiny dahlias out?

We are having temps of 40s at night and 70s during the day. I left two boxes of them outside and
they seem all right. Should I bring them back inside; it does stay cool at night (on average) until
the middle of the summer.

I would keep them iniside. You need to gradually get them use to outdoors. 30 degrees is way to cold for young seedlings.

'Stay Happy and Keep Gardening"

I would bring them inside during the period that it was in the 30s, but I would put them back out when it was warmer later in the next day. These seedlings right now were started in wet paper towels. I remove them the instant they germinate (that is I can see
the tiny, tiny white radical root emerging.) I put them in group containers and soon plant
them out in some kind of shoebox (plastic) or plastic bin. So really they are being protected by moving them inside. Also I use Remay (the non woven fabric like a row cover) to give me a 6 degree protection compared to the outside temperatures. Well,
I may lose some; but I think I have it covered. They are so young, they don't know what
real dahlia temps should be like. LOL. I know that's not scientific. If we get a severe cold snap, they will come in until the temps moderate.