What are the characteristics of the overwintering sites in Mexico?

Monarchs in Mexico overwinter in the Transvolcanic mountain range of central Mexico in high-elevation oyamel fir forests. Typically, their preferred locations are about 2 miles (3,000 meters) above sea level. These sites are typically found on moderately steep south-southwest facing slopes and near a stream or source of water. The temperature at these locations is fairly cool, typically just a bit above freezing. It can get warmer during the day, but nights remain fairly cool.