Winter parking restrictions will begin on November 1 and will remain in effect until April 1. During this time, parking on city streets and alleyways is prohibited from midnight to 7 a.m.
The parking restriction allows the City to thoroughly plow the streets during snow events and remains in effect even if it is not snowing to aid in street sweeping. This ordinance is enforced by the Flagstaff Police Department. Cars that are parked in violation of the ordinance when it is not snowing will receive a ticket and those parked in violation during inclement weather will receive a ticket and could be towed.
Original source can be found here.