March 11, 2016
A winter storm of historic proportions has struck the monarch sanctuaries in Mexico. There is no word yet about how the monarchs were affected. However, the sequence of events is of particular concern. The storm began with rain and was followed by hail, snow, and sub-freezing temperatures. The butterflies are more susceptible to mortality from freezing when wet. Photos from El Rosario Sanctuary show trees within the sanctuary core zone toppled by the strong winds. Spring migration from Mexico was imminent but mass departure had evidently not yet occurred meaning the full population was in the storm's path.

March 15, 2016 Update: Impact of the Storm