Is it an effective technique for grass? Worked great for the beans and hydrangeas.

I do it on any plant showing signs of heat stress. Our flowers requires multiple watering per day. For the lawn I would target something more than 5 minutes since the sun may simply evaporate that quickly. Just up it to half inch every few (3-4) days versus once a week, especially if in the high 90s. We only get heat like that one or two times a summer. In warmer climates you may consider dormancy for a month with minimal watering to keep it alive but brown.

It works. Golf courses use it on greens to keep them from getting too crispy. For the home owner, I'd say it's more cosmetic than anything. Unless you have a water system, it wouldn't be worth the labor. In my opinion,, it may promote disease and really doesn't do much for the health of the turf. I'd recommend sticking with deep and infrequent.

I saw an ad the other day for a diluted sunscreen for grass on golf courses that helps reduce the heat. I have Bermuda so that seems ridiculous to me, but I can see the use for heat waves up north

I did about 3 rounds of 10 minutes watering today, one around 11, one around 2 and one around 4. The issue is not with soil moisture, there's plenty of that, but whether the quick shower would help with heat stress like it does other plants. Obviously I have no idea if it did anything or not as far as helping the plant, but measured with an IR temp gun it lowered the temperature at the surface by about 10 degrees during watering and for about 5 minutes after (unrelated to the watering, the lawn is about 30 degrees cooler than the cement driveway).

I've had to spray the hydrangeas and beans again today and they responded again to the quick shower, but there's other plants that just take the sun with no problem: cucumbers, tomatoes, bell peppers, all showed no sign of stress within 10 feet of the beans. Without a control area, there's no way to know whether the grass benefits from this practice or not. There's probably down sides to it - had I not just sprayed serious fungicides I'd be concerned about fungus. Also had I not applied pre-emergent this spring I'd be concerned about germinating weeds. But under these circumstances I may do it again during periods of high heat, if only to lower the canopy temp by 10 degrees for 15 minutes.

Check the label on your serious fungicides to see if there are temperature limits. One of the reasons it's hard to control fungus disease in Texas is the temp is above 85 a lot of the time.

Otherwise misting the grass might help if you see it wilting. As long as you're not trying to saturate the soil it should be helpful. Do you need to do it multiple times a day?

Some plants are subtropical. Tomatoes and peppers are examples. Some are arctic. The piggyback plant comes to mind as a native of the Alaskan latitudes.

There's definitely temp limits on the serious fungicides but I applied them in the evening in cooler temps. No issues yet.

Edit: in regards to wilting, I don't se any wilting on the grass yet. I watered deeply Friday and it's holding up surprisingly well. Just thought I'd mist it as additional help in battling heat stress.

Here's where I'm at so far, I took some losses due to fungus. Last year it was all gone by June 1st due to poor management on my part. I'm determined to fight the odds this year. Did someone say sunscreen?

You can even see the drooping hydrangeas cooking in the full sun.

Oddly enough there does exist a sunscreen for grass called turfscreen. Seems questionable to me, but hey I've been wrong plenty in my time