Effective from May 1st to October 1st, Watering two days a week should be sufficient during most of the summer. If needed, water a third day during extreme heat or dry periods. Water trees and shrubs as needed, but not between 10 a.m. and 6 p.m. Shrubs and perennials need half as much water as lawns. There are no assigned watering days, but never water more than three days a week.
Story via Denver Water
