Syracuse, NY · 13201
Lawn watering need this week
Set your controller to
0.49 - 0.83inches this week
- 0.49 in
- Keeps it alive. UC ANR is blunt about this level: expect “many brown areas, considerable thinning out, and little growth” under stress.
- 0.83 in
- Full replacement. Keeps good quality turf green and growing through the week.
Total for the week, split across the days you already water. 0.14 in of rain fell here in the last 7 days and has already been deducted.
Your grass
Bermuda, zoysia, St. Augustine, centipede
Your sprinkler heads
Gear-driven heads that turn, throwing 25 ft or more. Best case for a home system.
How that number is built
1. Water lost from a reference lawn, last 7 days
1.209in ET0
Measured for Syracuse, NY from heat, wind, humidity, and sunlight combined, using the FAO-56 Penman-Monteith equations.
2. What your grass actually uses
0.72in
1.209 × 0.6, the crop coefficient for warm-season turf published by the UC ANR Center for Landscape & Urban Horticulture. This is what the plant transpires. It is not a controller setting.
3. What you have to apply to deliver that
0.49 - 0.83in
Rain first: 0.14 in fell in those 7 days and counts toward what the plant needed. What is left is divided by 70% system efficiency, because no sprinkler puts every drop where the grass can use it. Colorado State Extension puts spray heads at 50%, small rotors at 65%, and large rotors at 70%, and notes most untuned home systems run 30% to 40%.
The low end uses 0.4 and the high end 0.6, UC ANR’s minimal and good-quality coefficients for warm-season turf.
Want this exact, instead of from a table?
A catch cup test measures what your heads really put down on your lawn, which beats any efficiency estimate.
Run a catch cup test →Is this a normal week?
5.5% above normal
1.209 in ET0 this week against 1.146 in for the same seven calendar days averaged over the past 5 years here. Both sides are ET0, so this comparison holds no matter what grass you have or how good your sprinklers are.
Already have a weekly number you trust? Move it up 10% and check again in a few days, rather than jumping the whole way. Colorado State describes this as the Percent Key on most controllers, adjusted “in 10% increments.”
Check another ZIP
Why every source gives you a different number
Search how much to water a lawn and you will get one inch a week, an inch and a half, half an inch twice a week, and a rule about wetting the soil six inches deep. It reads like the experts disagree. They mostly do not. They are publishing three different quantities, and a fixed inches-per-week figure is only ever correct for the climate it was measured in.
The three quantities
Step 1
Water lost from a reference lawn (ET0)
How fast water leaves a well watered patch of grass, from heat, wind, humidity, and sunlight combined.
Never a controller setting on its own. It is the raw weather measurement everything else is built from.
Step 2
What your grass uses
ET0 multiplied by a crop coefficient for your grass type. Warm-season turf uses about 60% of ET0, cool-season about 80%.
Still not a controller setting. This is what the plant transpires, assuming every drop reaches it.
Step 3
What you apply
What the grass uses, divided by how efficient your sprinklers are. Always the largest of the three.
This is the controller setting. It is larger than plant need because no sprinkler is perfectly even.
Mixing these up is the single most common way a lawn gets underwatered on a schedule that looks correct. Setting a controller to the plant-need figure runs a deficit of roughly a third on a good system, and more than half on a poor one.
The same advice, read properly
| Source | What it says | What it is actually measuring |
|---|---|---|
| Colorado State Extension | 1.5 inches a week in July and August | Applied water including rainfall, for Colorado's climate and its predominantly cool-season lawns. |
| Clemson Extension | About 1 inch on heavy soil, half an inch on sandy soil | Depth per application, chosen to wet the soil 4 to 6 inches deep. Not a weekly total. |
| UC ANR | 60% of ET0 for warm-season turf, 80% for cool-season | What the plant uses, as a fraction of the local weather measurement. Scales to any climate. |
None of them is wrong. They answer different questions. This page starts from the weather at your ZIP instead of a national average, which is why its answer moves week to week when theirs cannot.
Change minutes, not days
When a week runs hot, make each watering longer rather than adding another watering day. Clemson Extension: “Watering every day with a small amount will encourage a shallow root system, making the grass less drought tolerant.” Deep and infrequent is what drives roots down, and roots are what carry a lawn through the next hot stretch.
If water runs off before it soaks in, split a single watering into shorter bursts with soak time between them rather than watering on more days.
Move in 10% steps
If you already have a weekly number that has been working, do not throw it out for this one. Move it 10% at a time and watch the lawn. Colorado State describes exactly this control, the Percent Key found on most timers, adjusted “in 10% increments.” Stepping means one odd week or one bad reading costs you 10%, not everything.
Where these numbers come from
- Reference evapotranspiration: Open-Meteo, computed with the FAO-56 Penman-Monteith equations for a well watered grass surface.
- Crop coefficients: UC ANR Center for Landscape & Urban Horticulture turfgrass Kc tables, annual averages for good quality turf.
- Sprinkler efficiency and the 10% stepping guidance: Colorado State Extension.
- Watering frequency and rooting depth: Clemson Extension Home & Garden Information Center.
Estimates from tables get you close. A catch cup test measures what your own heads actually deliver, and beats every assumption on this page.
Get the app and let it run your season
Free to download on iPhone and Android.