Hello Paul,

Unfortunately, the two closeup photos show damage that is consistent with skunk or racoon digging that results from foraging for grubs.  Do you apply regular irrigation?   When grubs feed on the roots of the lawn, they leave what is essentially "sod" atop the soil - there is a small root mass, but nothing deep.  This is significant in two ways.  Much like sod, if you keep the lawn watered, and there is not a lot of heat stress on it, it can look fine until that sunny hot day where it all seems to die at once.  There is just not enough root mass to hydrate the grass plants.

The other effect of grub feeding is that you can literally grab the grass and pick it up like it is just laying on top of the soil.

This article is excellent for explaining how to do a "test peel-back" of a grass area and check for grubs.  It also addresses the curative pesticides that can be used for killing feeding grubs that do the damage, as well as the preventive pesticides that will kill beetle egg hatchlings that would otherwise grow into this fall's feeding grubs.  https://www.canr.msu.edu/news/how_to_choose_and_when_to_apply_grub_control_products_for_your_lawn

If you do a test peel and find grubs, and would like some more specific information on pesticide use, please answer back.

Hope this helps.

Sure.

If you report back your findings, I can steer you toward a treatment plan.