When to Water Your Lawn: Times, Frequency, and the Tuna Can Test

Updated September 2026 · 8 min read

Most lawn watering is wrong in one of three ways: wrong time of day, too frequent, or too shallow. Here's the actual schedule that builds deep roots — and the $0 test that proves it.

Quick Answer: Water 1–2x per week, 25–40 minutes per cycle, between 4 and 9 a.m. Deliver 1–1.5 inches per week total, including rain. The tuna can test tells you exactly how long your sprinklers need to run to hit that.

The Tuna Can Test (5 Minutes, Free)

1. Place 5–6 empty tuna cans (or rain gauges) across one sprinkler zone
2. Run the zone 20 minutes
3. Measure each can. Uneven depths = uneven coverage — adjust sprinkler heads
4. Compute: if cans average 0.25" in 20 min, you need 60–80 min weekly for 1" — split across 2 waterings

Why 6 a.m. Wins

• 4–9 a.m.: least evaporation, water soaks in before sun, grass blades dry by morning — fungus risk lowest.
• 6 p.m.: blades stay wet overnight = fungus city (brown patch, dollar spot).
• Midday: up to 40% of water evaporates before soaking in.

Frequency by Season

Verdict

Water deep and infrequent — 1–2x weekly for 25–40 minutes beats 15 minutes daily, every time. Morning wins over evening on fungus alone. Run the tuna can test once; it takes 20 minutes and permanently answers "how long should I water?"