The answer to this question is “it depends.” Warm-season turf grasses can easily survive extended periods of drought by entering dormancy. It is okay to allow your grass to enter dormancy, provided you are prepared to see some wilt signs and browning of leaf blades.
If a period of limited or no rainfall or irrigation is prolonged, you can expect your lawn to thin out and possibly experience increased weed pressure. If your desire is to maintain a uniformly green lawn during drought, you will need to apply supplemental irrigation. However, the supplemental irrigation must be carefully monitored. Unless rain is forecast in the next 24 hours, lawns should be irrigated when 30 – 50 percent of the lawn shows signs of wilt. How long it will take your lawn to exhibit wilt to this extent will depend upon the climate of your area and the soil conditions in your yard. Caution should be exercised when applying weed-control products, as they may harm an already-stressed turf.