Monarch butterflies by the thousands overwinter near Pismo Beach and other areas in central California.
Monarchs are a tropical species, but they have found a safe place to overwinter here, and in several central California eucylaptus groves.
Colder weather inland would freeze them; warmer weather south would cause them to burn their stored fat supplies and they would starve.
They spend October through February here, then migrate as the weather warms up.