Well, while your soil type, the amount of sunlight, as well as the climate all enter into play, a great guideline is 1 to 1- 1/2 inches a week.
Let’s say you chose 1-1/2 inches a week, you can do it in one or two days. However, do not do just a little every day or daily. If you do a little each day your grass will have shallow roots and you can have all types of drought issues.
Now if you have sandy soil, it is best to sprinkle your lawn two times a week because sandy soil drains faster and the water ends up being too far down for your thirsty turf roots to reach it.
On the other hand, if you have completely dry clay dirt, you might need to water it 3 times a week due to its water-repelling qualities.
Let’s say you are uncertain just how much water your lawn sprinkler(s) put out in an hour, then you can put out a few plastic tubs to gauge just how much water your grass is getting, and after that, adjust your water time as necessary to the 1-1/2 inches.
Likewise, by putting out several plastic tubs, you can see if your sprinklers are sprinkling the entire lawn evenly or not. Make sense?
So now you probably want to know when’s the best time to water?
The best, most effective time to water is early morning. If you wait until afternoon or mid-day, you lose some of your water to evaporation. If you water in the evening or during the night, you could be welcoming ill conditions to your lawn because of the length of time it remains damp.
So, here’s a couple of quick tips to ensure your lawn looks great when it gets really hot out. (1) Do not mow it too short and (2) leave the grass clippings on the lawn. Contrary to popular belief, grass clippings will not create thatch accumulation.
By increasing your mowing height, the lawn is less likely to become stressed from the heat and will be able to cool by itself. Also, those clipping that you leave on the grass will provide your lawn’s roots added moisture as well as minerals which will assist it to become less stressed.
Anyway, I hope you can see that your watering techniques are just as important as how much you water your lawn.