I tested four herbicides in hot weather for potential damage to grass. However DARN! Cool year--our first predicted 90 degree day of the year did not happen, as it rained. Temperatures remained about 85 and then fell to about 80 in the next two days. I used: a 3-way, Surge, Speedzone, and T-Zone, each with surfactant, except the 3-way which was a ready to use spray bottle. I used approximately label rate and applied to7 inch diameter circles, one time, three times over and 5 times over. I calculated it at about a half-gallon per thousand sqft as the water rate. I applied to bluegrass/ryegrass mixture in light shade, and in a second area, Bermuda in a full-sun area. After 72 hours--no injury to either species of grass was visible. Stay tuned.