The short answer
Generally no. An established lawn goes brown and dormant in drought and recovers when the rain returns. If you do water, water deeply and rarely rather than lightly and often.
- Brown is not dead. Established grass goes dormant to survive drought and greens up within a fortnight of proper rain.
- If you do water: a good soak once a week, enough to wet the soil several centimetres down, rather than a light sprinkle daily.
- Water early morning or evening, not in the middle of the day.
- Raise the cutting height through a dry spell, and cut less often.
- New turf and new seed do need watering. Established lawn does not.
What will ruin it
Light frequent watering is worse than none. It encourages shallow roots that then die the moment you stop, which leaves a lawn less drought-tolerant than it was before you started.
Why it works
Roots grow towards water. Deep infrequent watering pulls roots downwards where the soil stays moist; daily sprinkling keeps them in the top centimetre where they cook.
Tipking is general household information, not professional advice. Test anything on a hidden patch first. Full disclaimer.