I put mine out when there's no chance of frost, and when the nights are above 50*. Ideal temps are between 50-80*. Mine are going out now. I'm in zone 7b, NC.

Agree w Kasha77. > 50 °F is best.

I'm in z8b and I put my larger ones out a week after the first average frost free day. They were stored quite dry all winter both in a garage with an average minimum temperature of ~40 °F or in a heated and lighted plant shed next to a sliding door with 50 to 60 °F night temperature. We've been running 36 to 48 °F nights since with a lot of rain and they are doing great and starting to grow fine. So they can take cooler nighrs.

I am in the Twin Cities (MN) Zone 4A, last year I put mine outside, which were overwintered in my basement, around 4/16/17. I believe we had some nights in the upper 30's those first few weeks- and mine were just fine. These pictures are from July and Sept.

LongfellowMN thx so much am emcouraged.