Mid-day watering won't hurt your lawn but you may need to do it longer as you'll lose moisture to evaporation.

Is watering lawn midday bad?

Avoid watering during the middle of the day when the heat is highest, it isn't the best time to water, and you can lose up to about 65% of water through evaporation, but are you going to burn the lawn? No. You are more likely to burn the lawn with too much fertiliser than too much water.

Does grass burn if you water it in the afternoon?

Avoid peak temperatures between noon and 2 p.m. and water in the mid-afternoon if morning isn't an option. Does watering grass in the sun burn it? Although dry grass can scorch, watering it in the sun doesn't burn your lawn. The concept of grass burning in the sun due to water droplets reflecting light is a myth.