MEXICO CITY — Storms this year blew down more than 100 acres of forests where monarch butterflies spend the winter in central Mexico, killing more than 7 percent of the monarchs.

Rain, cold and high winds from the storms caused the loss of 133 acres of pine and fir trees in the forests west of Mexico City, more than four times the amount lost to illegal logging this year. It was the biggest storm-related loss since the winter of 2009-10, when unusually heavy rainstorms and mudslides caused the destruction of 262 acres of trees.

A guide holds up a damaged and dying butterfly at the monarch butterfly reserve in Piedra Herrada, Mexico State, Mexico, last November.

This year’s storm also appears to have frozen or killed about 6.2 million butterflies, almost 7.4 percent of the estimated 84 million butterflies that wintered in Mexico, said Alejandro Del Mazo, the attorney general for environmental protection.

“Never had we observed such a combination of high winds, rain and freezing temperatures,” monarch expert Lincoln Brower said of the storms, which struck March 8-9.

Two big storm losses within five years may suggest changes in the climatic conditions that have allowed the survival of patches of mountaintop forests. An additional 16 acres of trees were lost to drought this year.

The monarchs depend on finding relatively well-preserved forests, where millions of the orange-and-black butterflies hang in clumps from the boughs.

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