I receive updates from both Missouri and Kansas State turf programs and extension. There was an interesting posting from Kansas State regarding irrigation of home lawns.
Right now, if you have a cool season lawn, you should be doing nothing to the lawn except applying some water from time to time to keep it from going dormant. Heavy, saturated watering leads to more weeds outpacing your turf this time of year.
Also, nutsedge is everywhere. Spraying during this type of heat might kill the water grass but will kill everything else. We have a fine crop on the golf course right now that will continue to grow until the weather cools to more normal or less than normal temperatures. I missed my window earlier in the season to eliminate some of this dastardly stuff and refuse to damage good turf just to reduce its existence. This season, it has won but there is always next year and we will be applying early and often before the heat.