Monarch butterfly migration is the phenomenon, mainly across North America, where the subspecies Danaus plexippus plexippus migrates each summer and autumn to and from overwintering sites on the West Coast of California or mountainous sites in Central Mexico. Other subspecies perform minor migrations or none at all. This massive movement of butterflies has been called “one of the most spectacular natural phenomena in the world”.

Monarch Butterflies are very sensitive to changes in temperature as
they rely heavily on this factor to prompt migration, hibernation and
reproduction. Thus, changes in temperature due to climate change are
expected to influence and potentially disrupt these critical stages of the
butterflies’ life cycle. For example, it has been discovered that exposure to
cold temperatures at the overwintering sites is the key factor in determining
a switch in the direction of the migration from southward to northward
in overwintering butterflies.