S l o w d o w n watering for established trees, shrubs, ground covers, lawns, and potted plants for Fall and Winter. Once a week was appropriate in warmer temperatures, but I would water on average once every two weeks through November, and then turn off the sprinkler for December and January.
If we go 3 weeks with no substantial rain, then water beds and lawns thoroughly one time. If freezing temperatures are in the forecast, run the sprinklers the previous afternoon to add heat to the soil and fill air spaces in the soil with water to exclude the cold air.
Newly planted trees and shrubs, newly potted plants, and winter annual flowers and vegetables in active growth will need more regular watering, and may be particularly sensitive to a cold, low-humidity dry norther. If there are zero clouds in the sky, and you are licking your lips, and there is a stiff breeze blowing, that dry breeze can necessitate watering despite the cool/cold temperatures.
Slowing down watering in Fall will slow metabolism in your trees, shrubs, groundcovers, lawns, and potted plants, and this makes them more tolerant of a freeze. Also, excessive frequency of lawn watering in Winter makes grass more susceptible to Take All Root Rot fungus. So, use appropriate watering as a sound gardening tool.
-James Gill