I think you are talking about red thatch or red thread disease in your lawn. 

If so, this is a fungus and not surprising given the amount of rain we have had this spring and early summer. It can occur because of low nitrogen levels. The best time to fertilize your lawn is in the fall. We don’t recommend it during the heat of the summer and we are now moving into a warm dry spell (we think).

I doubt that your in-ground sprinklers were running much so far this year. With all of the rain we have had it has been difficult for the grass to dry out. It is normal and healthy for grass to dry out between rain events. 

The ideal time for your sprinklers to run is at about 4:00 am - before the sun is up so that the water soaks in and the blades dry off in the afternoon sun.

Below is some information that should help. Be sure to read the section on water-saving strategies.

https://apps.extension.umn.edu/garden/diagnose/plant/turf/discolored.html

https://extension.umn.edu/lawn-care/auditing-home-lawn-irrigation-systems

https://extension.umn.edu/lawns-and-landscapes/lawn-care