Trees should be watered during dry, hot periods when there is no rainfall for two weeks. The equivalent of 1 inch of rain per two weeks would be sufficient. Water can be measured with a rain gage or straight sided container placed in the watering area. Properly watered trees are healthier and therefore are able to resist pests and diseases better.
Along with watering it is important to look at the leaves of your trees. Problems may exist if the leaves have holes or are shriveling, dropping, turning brown, yellow or onto early fall color. Consulting an Arborist when these signs appear is the best way to treat the problem and hopefully minimize the damage.
Trimming of your trees (except the Elms & Oaks) is good to do during this time to help prevent damage from storms. Cleaning up the dead wood, any broken hanging branches and thinning up the ends of the branches will help to minimize damage that may occur.