View & Download Western Monarch Count Data
The Western Monarch Count is a product of annual monitoring efforts at monarch overwintering sites.
Each year between October and March, community scientists and conservation professionals collect data at monarch overwintering sites located along the California coast, Northern Baja California and a few inland sites in California and Arizona. Decades of data from this community-powered initiative highlight the steep decline of migratory western monarchs. These data are compiled and entered into the Xerces Society’s Western Monarch Overwintering Sites (WMOS) database which also includes historic observations prior to 1997 when the WMC began. A public summary of WMC data is available below; this data summary is updated each season once survey data are vetted.
LINK: Monarch overwintering sites
LINK: Download data for all years (1997-2026)
Data Citation: Xerces Society Western Monarch Count. 2026. Western Monarch Count Data, 1997-2026. Available at WesternMonarchCount.org.
LINK: WesternMonarchCount.org
*NOTE: The public dataset was last updated on February 26, 2026. If you are a researcher using this data, please be aware that the download function above offers a static version of a subset of data.
Results from the 2025 mid-season Western Monarch Count
Approximately 12,260 monarchs were recorded across 249 sites during the typical peak overwintering period from late November through early December 2025. For an overview of the 29th annual mid-season count (formerly called “Thanksgiving count”), read the Xerces Society’s Press Release (in Spanish here).
LINK: Xerces Society’s Press Release
LINK: In Spanish here
Announcement webinar recording from January 29, 2026:
Data Citation: Xerces Society Western Monarch Count. 2026. Western Monarch Count Data, 1997-2025. Available at WesternMonarchCount.org.
LINK: WesternMonarchCount.org
Results from the 2025-26 late-season count
The final survey period of the Xerces Society’s Western Monarch Count ended on January 11, 2026 after volunteers and partners recorded 6,464 monarch butterflies across 193 overwintering sites. This tally is 47% lower than the mid-season count of 12,260 butterflies, compared with 35%-58% seen in the past ten years. A drop between the mid-season to late-season counts is typical due to seasonal mortality and possibly early dispersal from overwintering sites. Read the announcement summary here.
LINK: Read the announcement summary here.
These counts are possible thanks to the regional coordinators, volunteers & conservation partners who spend countless hours surveying each year. THANK YOU to all who participate in this invaluable community science project!
Notice: Below is a list of 7 important links included on this page.
1. Monarch overwintering sites
2. Download data for all years (1997-2026)
4. Xerces Society’s Press Release
7. Read the announcement summary here.
Please note that while screen readers have made significant strides, they may still lack full support for optimal web accessibility.
The Western Monarch Count is a product of annual monitoring efforts at monarch overwintering sites.
Each year between October and March, community scientists and conservation professionals collect data at monarch overwintering sites located along the California coast, Northern Baja California and a few inland sites in California and Arizona. Decades of data from this community-powered initiative highlight the steep decline of migratory western monarchs. These data are compiled and entered into the Xerces Society’s Western Monarch Overwintering Sites (WMOS) database which also includes historic observations prior to 1997 when the WMC began. A public summary of WMC data is available below; this data summary is updated each season once survey data are vetted.
Data Citation: Xerces Society Western Monarch Count. 2026. Western Monarch Count Data, 1997-2026. Available at WesternMonarchCount.org.
*NOTE: The public dataset was last updated on February 26, 2026. If you are a researcher using this data, please be aware that the download function above offers a static version of a subset of data.
Results from the 2025 mid-season Western Monarch Count
Approximately 12,260 monarchs were recorded across 249 sites during the typical peak overwintering period from late November through early December 2025. For an overview of the 29th annual mid-season count (formerly called “Thanksgiving count”), read the Xerces Society’s Press Release (in Spanish here).
Announcement webinar recording from January 29, 2026:
Data Citation: Xerces Society Western Monarch Count. 2026. Western Monarch Count Data, 1997-2025. Available at WesternMonarchCount.org.
Results from the 2025-26 late-season count
The final survey period of the Xerces Society’s Western Monarch Count ended on January 11, 2026 after volunteers and partners recorded 6,464 monarch butterflies across 193 overwintering sites. This tally is 47% lower than the mid-season count of 12,260 butterflies, compared with 35%-58% seen in the past ten years. A drop between the mid-season to late-season counts is typical due to seasonal mortality and possibly early dispersal from overwintering sites. Read the announcement summary here.
These counts are possible thanks to the regional coordinators, volunteers & conservation partners who spend countless hours surveying each year. THANK YOU to all who participate in this invaluable community science project!
