The P. tomentosum is looking a bit miserable at the moment. Just in the last week the leaves have started to curl up slightly. Now it was a bit dry so I've given it a watering, but the leaf curling has coincided with a slightly cooler period of weather. Nothing anywhere near frost, but I think one night it may have dropped to about 9 degrees.

Does anyone else have this type of pelargonium and have you noticed it being a bit more tender? For that matter, how do ivy-leaved pelargoniums normally fare in comparison to the zonals? I've only overwintered the zonal before, I've had those a few years and just stick them in a cold greenhouse and don't water much if at all. Some people seem to get away with keeping them outside all year here if in something like a windowbox, although they end up looking tatty.

I have left P. tomentosum out in a pot with a bit of bubblewrap over it and they made it through, but again, very slow to come back. Last winter they didn't make it, but no worries, I DID have cuttings of that because it is too gorgeous to be without. I find them quite prone to wilting which surprises me because they look very drought resistant. I do cram them into pots, though, maybe that's why.
To answer your question, I don't think the temps we have had so far would bother it, it would take a proper 0 degree or less one to kill off the tops.