I am doing the lawn detective thing again today and we are going to talk about heat stress in lawns. This isn’t what I’d call a “big problem,” but it is something I run across quite often during the summer and into the fall time.
What Is Lawn Heat Stress?
Lawns in the Midwest are usually made up of Kentucky Bluegrass, Perennial Rye Grass, Turf Type Tall fescue or some combination of them. There are other types I find, but these are the majority. These grass types do well here because of our seasonal changes.
Heat stress along the "hot zone"
However, they cannot handle super hot temps sustained. It doesn’t matter how much you water your lawn, when it gets over 95 degrees for long periods of time, your northern turfgrasses will go brown and dormant (dormant lawns are NOT dead, they are just not growing… it is a natural defense mechanism). If the heat persists for over a month or so, you could even get some slight die-back in the turf… but not anything to worry about in most cases.
Now here is the issue: There are “hot zones” in every lawn, and those are where we see a lot of heat stress during the summer and into the fall time. See the picture here. If you look, you can see that ALL the lawns all the way down the street are stressed at the curbside. This is because in the days prior, the temps in the area were around 90 degrees and blaring sun. The cement curb heated up to well over 95 degrees I am sure and that heat radiated into the lawn.
The people on this street all have irrigation systems and have them set properly. So while the rest of the grass is green, only the street side area is still brown and dormant. This is very normal.
The Fix?
Patience! All they need to do is continue watering like normal and allow that area of the grass to come out of dormancy. There is no longterm damage here… the lawn just went into dormancy due to the radiate heat. Pretty simple here for the lawn detective! 
