Avoid water application in the late afternoon, so that the plant foliage is dry going into the night. The less the foliage is wet the smaller chance there is of plant disease problems on turf, vegetables, or flowers.
Watering during the early morning hours has several advantages. There is less wind to affect the soaker hose, drip or sprinkler pattern. Plus, the temperatures are lower in the early morning, meaning more water gets into the soil and doesn’t evaporate away.
During hot summer days, plants will wilt severely on a hot afternoon. In that case, water them to revive them. Plants are not usually injured by watering in the heat of the day, but some plants may be burned by water remaining on leaves in bright sunlight. If you have an automatic system, anytime between 5 a.m. and 10 a.m. is a good time to irrigate.