On December 12, 2025, Pacific Grove Museum monitors counted 226 monarchs at the Monarch Grove Sanctuary on Ridge Road, the high point of the season. Two weeks later the count was in single digits. By January 17 it was back to 203. The butterflies had never left. A Christmas windstorm had broken up the clusters, and once the monarchs were spread through the trees in ones and twos, they were very hard to count.
That sequence comes from the City's 2026 assessment of the sanctuary and George Washington Park. Stuart Weiss of Creekside Science wrote it after site visits through the 2025–26 season and meetings with City Arborist John Kelly and environmental manager George Fuerst in January and June 2026. Weiss has worked at the grove since 1997. Read alongside the weekly numbers the Pacific Grove Museum of Natural History posts, his report suggests a different way to follow the season that is about to start. When only a couple hundred butterflies are present, the count describes the weather in the grove almost as much as it describes the population.
Where the Clusters Sit Depends on the Wind
Monarchs spend the winter in coastal groves that are sheltered from wind and get sun or dappled light. Weiss describes them as "crowdsourcing the microclimate": they leave spots that are too warm, too cool, too sunny, too shady, or above all too windy, and they land where other monarchs are already clustered.
In practice, they usually start the season on the sunny South Edge of the sanctuary and move into the interior after southerly storm winds. The last two winters were mild, and they never moved inward. In 2025–26 they stayed on eucalyptus along the South and Southwest edges from arrival in early October to departure. Eucalyptus accounted for 94% of observations, pines for 5%, and Monterey cypress for 2%. The 2024–25 season followed nearly the same pattern.
Windier years looked different. In 2023–24 the clusters moved from the South Edge into the South Interior by mid-November, deeper into the Interior by early January, and over to the Driveway by February. In 2022–23 successive strong storms pushed them into the North Interior. Weiss says the apparent preference for pine and cypress in most years is a matter of shelter. Those species dominate the wind-protected interior, and the butterflies are not choosing them for any other reason. In some years they have also clustered just south of the sanctuary boundary, on a lone Monterey pine.
So the first place to look this season is the sunny southern side, among the eucalyptus. After a real storm, look farther in.
One Storm, Read Day by Day
Last winter was mild. Even so, a single wind event shows how fast the count can move. Here is the sequence, pieced together from the report's weather data from Monterey Regional Airport and the Museum's counts:
- Fall 2025. No sustained hourly winds above 20 mph, though many days were above 15 mph. The count climbed to 188 by mid-November.
- Mid-December. Numbers were above 200, with the peak of 226 on December 12.
- December 24–25. Hourly winds peaked at 29 mph, the strongest of the season.
- December 26. The count fell to 3.
- January 2. The count was back to 131, showing the monarchs had scattered and stayed.
- January 4–8. Several days of steady, moderately strong wind. The count fell to 25 on January 7.
- January 17. The count recovered to 203.
- Late January. Seven days topped 70°F. Warm weather prompts monarchs to come out of their winter dormancy, and the grove was empty by February 7.
Weiss writes that when only about 200 butterflies are present, missing a group of 5 to 10 changes the picture a great deal. Small clusters and single monarchs are hard to spot in a complex canopy during the morning hours when counts take place. He recommends watching in the afternoon in low years, when the monarchs gather to roost for the night. He also says the Museum's monitors are adjusting their methods, and he is careful to say this is no criticism of their skill.
For a neighbor who visits more than once, this has a practical side. A late-afternoon walk on Ridge Road a day or two after a wind event may turn up butterflies that the morning count missed.
Why Low Years Make the Count Jumpy
A swing from 226 to single digits would be impossible at the scale the grove once supported. The Xerces Society's Thanksgiving counts for the sanctuary show how far the baseline has fallen:
Thanksgiving count | Monarch Grove Sanctuary | California total | Sanctuary's rank in California |
|---|---|---|---|
1997 | 45,000 | 1,235,490 | 10th, tied |
2006 | 28,746 | 221,058 | 1st |
2022 | 15,960 | 335,479 | 4th |
2023 | 6,608 | 233,394 | 10th |
2024 | 228 | 9,119 | 12th |
2025 | 188 | 12,260 | 16th |
Weiss finds that numbers at Pacific Grove mostly follow the statewide population. Most of the forces behind the swings play out in the inland breeding range, far from the coast. He attributes the 96% crash of 2024–25 mainly to record heat across nearly all of the interior breeding grounds in June and July 2024. The Xerces Society called the 2025 statewide tally the third-lowest since counting began in 1997. Its spring 2026 outlook warned that low numbers could return this winter unless the breeding season went well.
The sanctuary's share of the county total has shifted too. From 2001 on, it held an average of 37% of Monterey County's Thanksgiving count. In 2025 it held 12%, and most of the county's monarchs were at the private site near Big Sur at Esalen. That record helps when a single week's number looks alarming.
What the Grove Looks Like Going Into This Season
Weiss recommends relatively little work for 2026, and nearly all of it addresses fire risk. A small fire on March 31, 2024 scorched a eucalyptus trunk, and the report points to an earlier fire in March 2023 as well. His first recommendation was to clear and spread out the bark, branches, and leaves piled along the South Edge in September. Some debris would stay on the ground, broken up by firebreaks several feet wide, so that butterflies that fall have something to climb back up. That South Edge, with its eucalyptus, is also where the clusters have spent the last two winters.
The other items include:
- removing hazard trees and branches as they are found
- cutting the large fallen tree in the interior down to the ground
- a pause on new tree planting, except for a double row of cypress along the hotel boundary in the northeast corner
- thinning the crowded cypress northeast of the nectar beds
- reworking the nectar beds
- caging oaks along the western boundary to protect them from deer
Our research found no public confirmation that the September debris work was carried out. The same task appeared in the 2025 recommendations and was not done that year. At the commission meeting on August 18, 2026, City staff said a walk-through of the sanctuary was scheduled.
At George Washington Park, the City's May 2026 draft forest plan set a work window from mid-September to early October. It also bars tree removal, pruning, and other disturbance from October 1 through April 30 to protect monarchs. That window has now closed. Volunteers there have spent many hours watering newly planted pines. Weiss recommends switching to deeper, less frequent watering so the roots reach deeper soil before irrigation ends. George Washington Park has recorded no monarchs at Thanksgiving in any year since 2014. Its last notable count was 61, in 2011.
The grove also borders private yards. A 2025 study led by S. Cibotti examined about 200 dead or dying monarchs found on January 25, 2024, on a private lawn roughly 20 meters from the sanctuary boundary. Ten butterflies were tested. They carried 15 pesticides or related compounds between them, an average of seven each, and the pyrethroids bifenthrin and cypermethrin were found in all ten. The researchers concluded that pesticide exposure was the likely cause. The source was never identified.
The Fall Calendar
As of September 19, the Museum's status page said no monarchs had reached Pacific Grove yet. It expects a slow trickle from mid-October and a peak around the end of November, and it will post counts weekly once the butterflies settle.
- October 7 and October 10: Monarch Docent training through the Museum. Part two meets at the sanctuary at 250 Ridge Road.
- October 17 to November 1: Early-season window for the Western Monarch Count.
- November 14 to December 6: Mid-season window, which includes the Thanksgiving count.
- November 28: "Monarch Magic!", a Science Saturday at the Museum, 10 a.m. to 3 p.m., with free admission.
- December 26 to January 10: Late-season count window.
Western Monarch Count volunteers register every year. The Xerces Society describes the commitment as 12 to 15 hours over fall and winter, including virtual and field training, an assigned site, and surveys done with a partner. At the sanctuary, Museum docents are usually on hand from 11 a.m. to 3 p.m., weather permitting, October through February. The grove is open from sunrise to sunset with no admission fee or reservations. Pets are not allowed, and parking is limited to nearby streets such as Lighthouse Avenue. In a year like the last two, start on the sunny South Edge, and after a storm come back in the late afternoon.
At Carmel Luxury Group, we follow Pacific Grove closely, from the grove on Ridge Road to the streets around it. If you own property near the sanctuary and want to talk through what living beside it involves, start a confidential consultation.
