It is generally better to water grass seed in the morning rather than in the evening. This is because during the day, the sun and heat can cause the water to evaporate quickly, leaving the grass seed with insufficient moisture. When you water in the morning, the grass seed has ample time to absorb the water and benefit from it throughout the day. Additionally, watering in the evening can leave the grass seed damp overnight, which can create an environment that is conducive to the growth of fungi and other diseases.