"Last Thursday, February 12th we had a sudden, quick, and intense hail storm. It hit a rather small area that included the Sierra Chincua. El Rosario and the communities around Angangueo were untouched.

"I met biologist Felipe Martinez at the Chincua colony on Sunday. He said there was some mortality of monarchs that afternoon and more overnight due to freezing temperatures. He showed me a picture of some monarchs grounded by the storm."

• Map of Region

Surviving Storms
Snow and hail are not uncommon for monarchs in the wintertime, and the butterflies can survive. If they can stay dry, they are less likely to freeze. If they can climb off the forest floor, they can avoid exposure to predators, rain, dew, frost and sub-freezing temperatures.

After a storm, the forest floor can be alive with shivering monarchs, warming their muscles so they can climb to safety.