It should withstand temps in the mid-40's easily. The leaves on mine don't show any effects until it goes below about 35 degrees.
Congrats on all your monarchs!
Sherry

It was mid 40's here last night and all the tropical looks fine...it's TONIGHT I am worried about. Freeze warnings in Minnesota. I will have to cover at least one patch for the remaining monarchs.

All the monarchs here this morning are gone now. Hopefully they are flapping south for their lives!

This is a good topic. I've been wondering about mine too since it's gotten down in the upper fourties at night once or twice. I want to try to dig them up and overwinter them inside (try try again). The forecast is for nighttime temps in the upper fifties but I wonder if it would be less of a shock if I just went ahead and dug them up now instead of waiting as long as I can. Mine didn't make any seeds.

Christie, that seems early...and what about my poor monarchs coming down from Minnesota? ;) (still have 22)

Last year, I dug mine up just before the first frost and they did beautifully....they were blooming most of the winter.

It was 36 here two nights ago and all my tropical looks fine. I'm hoping two get a couple more weeks out of them! Tropical milkweed has proven to be surprisingly hardy, Tony

I'd leave them outside until you just have to move them, Christie, like right before your first freeze.
You're right, Tony, they are surprisingly hardy. The tops of mine get killed back by our usually mild (occasionally as low as 24 degrees or so) freezes in December and/or January, but they come back from the roots in early spring each year, knock on wood!
Sherry

Brindle, I'm in central PA and your tropical milkweed will be fine. I have lots of it and have been growing it for about 5 years and mine never got bad until it actually got down close to freezing. I used to wonder the same thing, being that it's originally from a much warmer area, but I found out that it's a really tough plant. I even have occasional self-seeding.

I was getting to like those temps in the 80's, but now I'm afraid that they're pretty much gone for the year. Yesterday the high here was 58 degrees, and today it's 60. I'll look forward to some more days in the 70's here before it turns cold until next year. I'm not much of a winter person and always look forward to when the butterflies show up again. I love to watch them and of course raise them. Best of luck with your various species of milkweed.
Cathy