I have heard that watering your grass early in the morning before the heat starts is bad for your grass. And I have heard that watering your grass before it gets dark in the evening is bad for your grass. So when is the "optimal" time to water your grass ??
It depends on time of the year (and temp/humidity) and other factors.
The idea is to allow the water time soak down into the soil.
Before it can be evaporated by the sun (hot summer)...
but still allowing time for the sun to warm the ground.
So... I'll say that in most areas and in most conditions the best time
to water is early in the AM; ending about sunrise or shortly after.
I agree. If you water just before sunrise the sun will be up and nocturnal insects will be discouraged from settling in and the sun will be up before fungus can take hold. Winds will generally be at a minimum also. Watering late in the day encourages both of the turf cannot dry out before sundown.