Every winter, a migratory generation of Monarch butterflies, instead of migrating to Mexico, stop and overwinter along California's central coast.
They need cool but not cold weather; cold would freeze them, warmer would speed up their metabolism and they would starve.
They will stay until Late February or Early March, then migrate north and breed. The caterpillars feed on milkweed.
There will be several generations over the summer, then finally a migratory generation to head south again for the winter.
These are in Pismo Beach.