Your lawn
Your watering schedule
| Climate region | |
|---|---|
| Grass water use | |
| This month's water need | |
| Cycle-and-soak | |
| Peak month |
12-month seasonal plan
Minutes per zone on each watering day. “—” means no watering that month (rain covers it, or the grass is dormant).
| Month | Days / week | Min / watering day | Schedule |
|---|
Why this schedule
How the schedule is built
Climate sets the curve
Your ZIP maps to one of 18 US climate regions, each carrying 1991–2020 monthly normals (high/low temperature and rainfall) from NOAA's nClimDiv dataset. The Hargreaves equation — documented in FAO Irrigation and Drainage Paper 56 — turns temperature into reference evapotranspiration (ET0), the atmosphere's baseline thirst. That's why July asks for far more water than April, and why Phoenix and Seattle get completely different schedules.
Grass sets the rate
Not all grasses drink alike. Turf scientists express this as a crop coefficient (Kc): the fraction of ET0 the grass actually uses. Warm-season grasses run lean — bermudagrass around 0.60 — while cool-season grasses like Kentucky bluegrass and tall fescue run near 0.80. St. Augustinegrass (0.65), zoysiagrass (0.70), and centipedegrass (0.65) sit between, per the published turfgrass literature.
Heads set the clock
Minutes = inches of water needed ÷ how fast your heads apply it. Fixed sprays (~1.5 in/hr) finish in a fraction of the time of rotors or MP rotators (~0.4 in/hr). When sources disagree on a constant, this tool uses the agronomically defensible published value and says which one in the results' methodology note.
Soil and slope force the split
Clay accepts water at roughly 0.1–0.2 inches per hour — far slower than a spray head's 1.5 in/hr — so a single long run mostly runs off into the gutter. The fix is cycle-and-soak: cap each cycle at what the soil can absorb (from Hunter's maximum-application-rate tables, tightened on slopes), then wait about 60 minutes between cycles (Texas A&M AgriLife) for it to soak in. Sand, at the other extreme, needs more frequent but shorter waterings because it holds so little.
Rain and dormancy turn the tap off
Effective rainfall (USDA-SCS method) is subtracted before any runtime is computed, so rainy months and rainy climates schedule little or nothing. Warm-season grasses go dormant below about 50°F and cool-season lawns stop when the ground freezes — both schedule zero automatically.
Frequently asked questions
How long should I water my lawn each time?
It depends on your sprinkler heads and soil, not a single number. Fixed spray heads apply about 1.5 inches per hour, so 10–20 minutes is typical; gear-drive rotors apply about 0.4 inches per hour, so 30–60 minutes is typical for the same amount of water. On clay soil or slopes, split the runtime into short cycles (for example, three 4-minute cycles an hour apart) so water soaks in instead of running off. This calculator works out the exact schedule from your grass, soil, heads, slope, and local climate.
How often should I water my lawn per week?
Most lawns do best with deep, infrequent watering: typically 1–3 days per week in summer, less in spring and fall, and none when rain covers the need or the grass is dormant. Sandy soils need more frequent, shorter waterings because they hold little water; loam and clay hold more, so you can water fewer days. The calculator sets watering days from your soil's water-holding capacity and your weekly climate-driven water need.
What is cycle-and-soak watering?
Cycle-and-soak splits a watering day's runtime into several short cycles with a soak period (about 60 minutes) between them. It exists because clay and sloped soils absorb water far slower than sprinklers apply it: a spray head at 1.5 inches per hour outruns clay soil, which accepts roughly 0.1–0.2 inches per hour, so a single long run mostly runs off. Short cycles let each dose soak into the root zone before the next one starts.
How much water does Bermuda grass need compared to fescue?
Warm-season grasses like Bermuda need roughly 60% of reference evapotranspiration (a crop coefficient of 0.60), while cool-season grasses like tall fescue and Kentucky bluegrass need roughly 80% (0.80) — so fescue needs about a third more water than Bermuda under the same weather. Zoysiagrass (0.70), St. Augustinegrass (0.65), and centipedegrass (0.65) fall in between.
Should I water my lawn in winter?
Usually not. Warm-season grasses (Bermuda, zoysia, St. Augustine, centipede) go dormant below about 50°F and need no irrigation while brown. Cool-season grasses need none when the ground is frozen. In mild-winter climates, winter rain normally covers what little the lawn uses. This calculator shows zero watering for dormant or frozen months automatically.
Is this calculator a substitute for a catch-can audit?
No. This is a planning estimate built on published precipitation rates, soil intake rates, and 1991–2020 climate normals. Real systems vary with pressure, spacing, and nozzle wear, so the definitive check is a catch-can test: place straight-sided cans around a zone, run it 15 minutes, and measure the depth caught. If your measured rate differs from the assumed one, scale the minutes proportionally.