Thousands of Monarch Butterflies Migrate to California Every Fall and Winter-How to See Them and Save Them

"Many (but not all) monarchs migrate seasonally, seeking refuge from too-cold temperatures. In Western North America, monarchs fly south from Canada and the Pacific Northwest to overwinter in temperate spots along the California coast. Some come from colder regions west of the Rocky Mountains, too. The overwintering season in California is roughly October to February. During this time, monarchs cluster together in packed colonies for warmth-in a good year, thousands of monarchs might rest on a single tree, creating a kaleidoscope of brilliantly colored wings."

"Sadly, monarch populations have been in a steady decline for years-and some seasons, including last year's, have brought extreme dips. For example, Pismo State Beach Monarch Butterfly Grove sheltered over 24,000 monarchs in 2022/23, over 16,000 in 2023/24, and then just 556 in 2024/25. The Xerces Society for Invertebrate Conservation, which organizes the official Western Monarch Count, cites climate change, pesticide use, and loss of overwintering habitat as reasons for monarch decline."

Monarchs in Western North America migrate south to overwinter on the California coast, with the season roughly October to February. During overwintering, monarchs cluster in packed colonies on trees such as eucalyptus, Monterey pine, and Monterey cypress to retain warmth. Overwintering aggregations can number thousands on a single tree in strong years, producing vivid displays. Monarch populations have declined steadily, with dramatic local drops such as Pismo State Beach counts: over 24,000 in 2022/23, over 16,000 in 2023/24, and 556 in 2024/25. The Xerces Society attributes declines to climate change, pesticide use, and loss of overwintering habitat. The 2025/26 migration season is underway, and coastal groves like Natural Bridges State Park, Santa Cruz, remain notable observation sites. Habitat protection, pesticide reduction, and landscape restoration can help bolster monarch numbers.

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