The best time to water the garden with a sprinkler irrigation system is under the following conditions:
The outside temperature should not be too high else the water will evaporate.
It should not be raining.
Early mornings before sunrise and late in the evening after sunset is the best time to switch on your automated irrigation system. In summer, this gap can be supplemented with a short irrigation cycle during the day either a few hours before noon and/or after when the sun is not directly overhead.