Monarch migration in New England usually starts aound the second week of September and continues up to about the second week of October. Notice what diection these gliders are heading. It's fascinating when you realize that all of these beatiful butterflies are no longer gliding in random directions in search of nectar, but rather gliding slowly but determinedly toward the south. If you don't know where south is, pull out a compass or locate the general direction of the sun in the sky toward the mid day hours. All the monarchs are heading in that direction. This past Thursday we had dozens of Monarchs feeding on nectar from our wildflower garden in front of the visitor center at Pinkham Notch, and more Monarchs can be seen passing through every day.
Photo: Monarchs feeding on Aster at Pinkham Notch
Their overwintering sites in the Sierra Madre are at close to 10,000 feet in elevation. Cool enough to keep their metabolism slow in order to preserve precious fat reserves, but usually warm enough to prevent deadly hard frosts due to the southerly location. The Sierra Madres are "just right" for an overwintering monarch, the only long distance migrant among the worlds butterflies.
AMC Natuarlist Guide