Dahlia foliage is very susceptible to frost, so if you do put them out, figure out how to keep them from freezing if we have a cold night. I'm planning on planting my tubers in pots outside in the next few days, though.

The gound temperature has to warm up a little before you can plant dahlia tubers. Hardening them off outside for a couple of hours on nice days wouldn't hurt them, but I wouldn't put them in the ground quite yet.

Memorial Day is usually my target date up here since we're still getting nights close to freezing.

It wouldn't hurt to start acclimating the plants to outdoor temps and especially the sun. Too much sun right away and the leaves will burn (turn a white color). I don't have dahlias, but all the plants I started from cuttings (Impatiens, geraniums) have been outside in their pots for about a week in a mostly shady spot with a few hours of morning sun.

I was at the arboretum today and noted that they have not even worked their big dahlia display bed yet.