I have heard several people comment that they do not spray weed at high temperatures for fear of turf damage and fear that the weeds would not be killed. Our neighbors to the south seem to think 90 degrees is fine. Therefore... I decided to test the theory on my vacant lot--I mean at the Micro Turfgrass Research Center. But then it got slight cooler so it was only a humid 93 degrees temperature at the time of the test and it has been about 90 to 92 as a high in the last few days. 33 degrees Celsius. Heavy rain a few days ago--soil was moist. Rye, blue and fine fescue. I sprayed a circle 13.5 inches in diameter, (equals one square foot). I sprayed spots for one second, 3 seconds and 5 seconds. Simulating about 1 times label rate, 3 times, and 5 times label rate. One second is about a third of an ounce of spray solution. I sprayed: Lesco Eliminate Gordon's T-Zone BASF Drive Thus far at 36 hours, no injury to the grass. Slight effects on the few weeds in the spots. I also treated poison ivy, and a few spots of weedy trees and brush nearby with Drive. Killed a few inches of a wild grapevine. Injured a bit of black locust. No visible effect on poison ivy, nor mulberry, nor box elder. Stay tuned.