Should You Water Your Lawn Today?

D.I.E.T. stands for Deep, Infrequent, Early, Track. The folk version of the rule is “one inch of water per week” — but that’s an average. What the lawn actually needs depends on heat, sun, and what the soil is already holding. So we use the real numbers, not the rule of thumb.

Soil moisture is the primary signal. We pull the current soil moisture for your ZIP from the same models the National Weather Service uses. If the soil sits in the Ideal band or wetter, the lawn has what it needs — hold off, regardless of how much rain fell this week. That’s the dial above.

When the soil dries back into the Dry or Drought range, we run a water balance: how much rain has fallen over the past 7 days, versus how much the lawn has lost to evapotranspiration (the FAO-56 reference ET that professional irrigation systems use). If rainfall has kept up with ET, no watering needed. If there’s a real deficit, we tell you the exact amount to add — usually less than an inch in spring, often more in summer heat.

If soil temperatures (averaged across the 6 cm and 18 cm probes, approximating the Purdue 4″ standard) are below 50°F, your grass is dormant — watering won’t help and we’ll tell you to put the hose away.