When you say really hot summer days, what are we talking about in terms of temperature.

In the desert southwest they sometimes syringe the lawn with a light spray - about 3 minutes. The main idea is to moisten the grass and let evaporation do the cooling.

Where do you live and what kind of grass do you have?

Sorry, I forget that my location doesn't show. I'm in SW Connecticut. I'm thinking when it's 85, 90 and the sun is really beating down (I don't have a lot of shade), it might make sense to cool it off a bit. But I have no idea if this is a good idea or bad idea.

Both Kentucky Bluegrass and Tall Fescue can take extended stretches (weeks) of 85-90 degree temps and full sun with no problem as long as it's got enough water in the soil. There's no need to syringe. If you have PRG, I'll deffer to others that know more about that grass type.

Thanks. I have a mix of KBG, TF and PRG. Though I'm trying to introduce more KBG and TF (no Rye) each time I overseed.