Major Monarch Highway
The Sierra Madres form a chain of north/south peaks and valleys that stand in the path of the easterly winds which predominate at this time of year. As the winds strike the ridges, the butterflies get a free lift.

From the Sierra Madres came a report of monarchs moving at a rate of 60 per minute — or 1 per second — the highest rate of the season.

Nuevo Leon: "El día de hoy que se despejo logramos observar 1,286 monarcas durante 20 minutos." October 24, 2014 San Pedro Garza García, Nuevo Leon

Only 300 Miles to Go
The southernmost peak migration report came from a valley only 300 miles from the overwintering region.

Tamaulipas: "Hundreds of monarchs feeding on sunflowers in the Sierra Madre Oriental on the border between Tamaulipas and Nuevo Leon. " October 22, 2014 Juamave, Tamaulipas

A Million Monarchs
The migration is so concentrated in the Sierra Madres that monarchs go through at exceedingly high rates. This is where the most spectacular sightings are possible. You might see a million monarchs one day — and none the next — in the very same place. Dr. Bill Calvert experienced a chance encounter in 2004.

"Seeing a million butterflies passing over is kind of magical." October 17, 2004 Cumbres de Monterrey, Nuevo Leon