The only thing that I can report is that mine agaist a south facing wall took temps. down to 20F for five night with no damage, but they were bone dry, even after the rain here when then get plenty of water, I haven't had any damage for the past 20 years. I haven't even noticed frost bite/burn on the leaves. Water is what kills them.
Read what the rest of the group write. Surely it won't be the same as I grow mine. I live in So. Calif. where we have dry weather. So because of this my cold may be different then others. LOL That's what they all tell me. Norma

Tom,

Highly coincidental that you mentioned that - I just ordered a new phonograph.

I would say not, but as Norma relates, these plants are fine if they're dry - it's when they've got the wet feet and it's near, at or below freezing that there's trouble. Well, your Madagascar plants would be dying in droves, as mine did one winter in SD when it was wet and cold, a combination of a heavy rain and cold-for-SD temps (below 5C/40F but not quite freezing) killed my Malagasy plants, mostly soft Kalanchoes, in droves. If you've never seen a melted Kalanchoe beharensis, let me tell you, it's a sad thing.

OTOH, the other plants, many of them New World Crassulaceae, simply dropped their leaves - their stems remained strong and they grew new leaves in the spring.

The regular green jade is the most frost intolerant, at 20deg it suffered badly but right next to was the variegated variety, not one leaf showed signs of damage. These plants had no protection and away from any structures.