The Right Time: If you must water, do so when evaporation rates are at their lowest. Any time during the period from a little before sunset to a little after sunrise is okay.The most desirable time for watering is within a couple of hours of dawn as the air and ground temperature are usually at their lowest point, allowing sufficient time for the water to get to the roots.Persistent watering during the late afternoon and evening, while allowing for the maximum time for water to get to the roots, could trigger a mold, mildew and other diseases, which could also kill your plants.
Water under wooded areas, too. With time, during dry periods, the ground under a canopy of trees will get just as dry as areas in the sun. The tree roots will draw upon that moisture in the shade.