Originally Posted by RigglePLC
Expert groundskeepers(like at baseball stadiums and golf courses), judge the need for water based on the appearance of the grass. If it starts to wilt, they start the irrigation. They have skill and a practised eye. Temperature is important, loss of water (evaoptranspiration) is faster at high temps, sandy soil, low himidity, or windy conditions.
You will get lots of opinions here. I would not worry about disease during hot dry conditions, even at night. Disease--especially red thread, dollarspot and brown patch--tends to occur during warm rainy humid nights. During dry spells you will only be wetting the grass for an hour or two.
I am not sure roots can sense where water is hiding. They mostly grow downward, and branch regularly. They will not penetrate dry soil.
I have a tuna can out right now getting a measurement. I will report back in an hr or 2. Its good to hear about not worrying about the disease this time of year. I dont water in the spring very much.