Better to water in early mornings if possible.
Biggest mistake with watering the grass is not doing it for long enough. People water for a short period and this just leaves the water in the top part of the soil resulting in the grass roots also going only that deep as that's there the water is.
Deep watering allows the water to go further into the soil forcing the grass roots to go deep and resulting in a healthier and more drought tolerant lawn.
Deep watering once a week should be sufficient. You want around 1-2 inches of water. Stick containers in various places the next time you do it and time how long it takes for them to get 1-2 inches of water in them from your normal watering. Water for that length of time in future.