View & Download WMC Data

The Western Monarch Count is a product of annual monitoring efforts of overwintering western monarch butterflies.

Data are collected from various overwintering sites located along the California coast, Northern Baja California, Mexico, and a few inland sites in California and Arizona. Thanks to the extraordinary efforts of hundreds of volunteers, we have over decades of data demonstrating that overwintering western monarchs have undergone a >90% decline since the 1980s. Data collected by volunteers are compiled and entered into the Xerces Society’s Western Monarch Overwintering Sites Database which also includes many historic counts and survey efforts. Contact [email protected] if you are interested in obtaining a copy of the entire database.

Download data for all years (1997-2024) *NOTE: If you are a researcher using this data, be sure you periodically check back to make sure you have the most recent version. Data were last updated on March 19, 2024.

Data Citation: Xerces Society Western Monarch Count. 2024. Western Monarch Count Data, 1997-2024. Available at

Results from the 2022 peak-season Western Monarch Count:

Volunteers counted 233,394 butterflies at 257 overwintering sites in the West. Read our blog for complete summaries of the 27th annual peak-season Western Monarch Count, which occurred November 11 – December 3, 2023.

Figure 1. Total monarchs reported and number of overwintering sites monitored for the peak-season Western Monarch Count from Nov. 1997 to Dec. 2023.

Results from the 2023-2024 late-season Western Monarch Count:

The late-season count revealed a 28% seasonal decrease in the overwintering western monarch population, less than the typical range observed over previous winters. A little over 141,000 butterflies were counted across 200 overwintering sites. Read our blog for complete summaries of the 8th annual late-season count, which occurred Dec. 23 – Jan. 7, 2024. 

Figure 2. Total monarchs reported and number of overwintering sites monitored for the late-season Western Monarch Count from Dec. 2016 to Jan. 2024.

These counts are only possible because of the incredible regional coordinators and volunteers that spend countless hours surveying overwintering sites each year. THANK YOU to all who participate in this invaluable community science project!