Laura,

I don't think the cold weather will hurt them, if it's not freezing. I had one spend the night in a sheltered area on my patio last night. When I moved the plants closer to house for protection, I found the Monarch on one of the leaves. I had released it earlier yesterday. Today it was gone. I also saw Monarchs flying south this morning when the temps were still pretty cool here.

It does get cold in Mexico where they are going. I've seen photos of Monarchs with frost on them. After the freezing temps here last night, there were still quite a few butterflies flying around today.

Having said all that, if it makes you feel better, keep them in the garage. They will be better prepared to take off in the morning (no warm up time required).

Sandy

I would wait til the morning to release them if I were you

I released them about 9 am this morning. Actually I carried them to a butterfly bush that was full sun and put them each on a bloom. They stayed there for some time, sunning their wings and slowly opening and closing them. They both flew away around noon.

~Laura

That is good to hear!

Best to release in morning.
Has to be 55 degrees for them to fly.