You can tell these monarchs are migrating and won't winter over. The butterflies that winter over won't come down to the shoreline; they'll stay inland. The ones we have here come in, feed on the bushes, and continue down the coast.

It was just migrating,

The gold-barr'd butterflies to and from And over the waterside wander'd and wove As heedless and idle as clouds that rove And drift by the peaks of perpetual snow. - Joaquin Miller (pseudonym of Cincinnatus Hiner Miller),

The trend is migrating outward.

In the winter you have warm, moist air going through the HVAC system coming out of a cool metal diffuser on a surface where it can condense and that can create an environment where it's possible for mold to grow.

Monarchs do this quite a bit but we don't how much they do it.