During the summer months, your lawn will require more water due to evaporation from the soil and transpiration (water loss through the grass blades). St. Augustine grass may die in less than 7 days in the absence of irrigation or rainfall. Every summer, we get calls from people who have turned off their irrigation system due to a rainy period, and forgot to turn it back on. A lawn may receive 20 inches of rain the month before, but it only takes a few days without rain or irrigation the month after to receive drought damage.
Unless you are committed to turning your sprinkler system on and off based on rainfall patterns, the system you use should have a rain sensor installed and left on automatic during the summer since our rains vary on frequency and amount of rainfall from week to week. Lawns should be inspected every couple of days during dry periods. You should also inspect your sprinklers as soon as possible at the first sign of wilt symptoms. You want to look for any possible irrigation system problems, and resolve them, and then apply water to the problem areas quickly to prevent expensive damage to the grass.