Photoperiod — the shrinking length of daylight after the autumn equinox — is the trigger that drops a doe into estrus and pushes a buck into seek-and-chase mode. Because day length on a given calendar date is identical from one year to the next, peak breeding in any given location is locked to roughly the same week every year. Weather and moon phase shift visibility and movement patterns within that window, but they do not move the underlying dates.
In practical terms, hunters in the Upper Midwest and Northeast see the most observable chasing the first two weeks of November. Mid-South states like Tennessee, Arkansas, and Georgia run a week or two later. Deep South states with year-round green vegetation can have peak breeding stretching from December into January, and parts of the Florida peninsula rut during summer.
The phases follow a consistent sequence — pre-rut, seeking, chasing, peak breeding (often called lockdown), and post-rut — though each phase blurs into the next on actual hunting ground. Bigger bucks tend to enter the seek phase a few days before younger ones because they are responding to the first does that come into estrus.
For the date range in your specific county and Deer Management Unit, see our state rut date pages for the exact peak windows derived from breeding-date studies.