November 2: "Today, the Day of the Dead, monarchs are massively arriving! Some popped-up yesterday, but the massive arrival is occurring right now. For us, the butterflies symbolize our ancestors' souls returning to Earth for their annual visit. A lot of people in town noted that monarchs had not been so precise in the last few years."
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Cerro Pelón Sanctuary
Dr. Ellen Sharp reported in from her home near the Cerro Pelón Sanctuary.

November 1: "My husband Joel, brother-in-law Vicente, and our five little nephews were jumping up and down and pointing at the sky. 'Monarchs!' And there they were, tiny black specks with furiously pumping wings flying high overhead, headed straight south of us. They started counting all at once...50! 60! At least a hundred!
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Sierra Chincua Sanctuary
Dr. David Mota-Sanchez reported news from his friend and colleague, Javier Castaneda.

November 2: "Exciting news! Today Javier witnessed an explosion of migratory butterflies, as thousands arrived at Sierra Chincua. Around 8:00 AM he saw the first ones flying at 300 yards above the ground at the sanctuary facilities. He saw more when walking to the Outlook Pena Blanca and el Zacatonal. The butterflies were flying in big circles very high above the tips of the sacred firs. Yesterday there were many monarchs in the valleys around the overwintering grounds, but today was the first big migratory wave." Read More...

Dr. Lincoln Brower, who has studied monarchs for decades, shared his amazement.

"It's astounding that they show up so regularly around the 1st of November. Suddenly, there they are, right on time. They just sweep into the area."

The first monarchs traditionally reach their winter home in Mexico by the first of November. How are Mexico's traditions connected to the monarch's arrival?

• Slideshow: Monarch Arrival and Mexican Traditions