If dry, then it's time you watered your lawn. Soil condition Different soils have different water holding capacity and porosity. It is very important to know your soil type and check soil moisture absorption and retention rates. Sandy soil is very porous and has very low water holding capacity while heavy soil absorbs slowly and holds water for a long period. Clayey soils also retain water for long periods.
Light soils absorb water faster but dry out quicker.
The plan of irrigation should be made according to the different soil conditions. Remember, the grass roots are down deep and most weed roots are near the surface. The idea is to keep the top three inches of soil as dry as you can for as long as you can. Frequent watering only becomes advantageous for the weed roots and they would love it more than anything. Apply water slowly and steadily ensuring that it reaches deep down to the roots helping in extensive root growth and does not run off.