A. Generally, rattlesnakes emerge from hibernation in March or April, or when the average daytime temperatures reach and remain about 60F and higher. The snakes are then most active when the temperatures are between 80-90F. This means that the snakes may be active most of the day during the spring, and during the early mornings and late afternoons throughout the summer. Exposure to temperatures above 110F for more than a few minutes is enough to kill a rattlesnake; therefore, during the hottest part of summer, snakes are seldom observed, except occasionally at night. Snake activity picks up again as temperatures begin to fall in late summer and early autumn before they go into hibernation as early as September or as late as December.