Should I water my lawn today?
We add up the past week's rain at your ZIP code, estimate how much water your lawn used in that weather, and check the forecast for rain in the next two days.
How the answer is worked out
Grass loses water through its leaves, faster when it's hot, sunny, dry and windy. We estimate that use from each day's high and low temperature (the Hargreaves method used by irrigation planners), scaled for mowed turf, and compare it with the rain that fell over the same days (PRISM daily data from Oregon State University). If the lawn is more than about half an inch short and no real rain is forecast, it's time to water.
- Rainfall varies from yard to yard: a summer thunderstorm can soak one street and miss the next.
- Sandy soil dries out faster than clay; shade and new seed change things too. New seed needs light watering every day until it's up.
- Watering restrictions in your town come first.
Fertilizing or seeding soon? Check your soil temperature and this year's lawn windows, or use the grass seed and fertilizer calculators.
Frequently asked questions
How much water does a lawn need per week?
About 1 inch a week in summer, counting rain, and up to 1.5 inches in very hot, dry weather. Warm-season grasses such as Bermuda and zoysia need less than cool-season fescue and bluegrass. In cool weather a lawn uses far less.
Is it better to water every day or once a week?
Water deeply and less often: one or two waterings a week that wet the soil several inches down grow deeper roots than a short daily sprinkle.
What time of day should I water my lawn?
Early morning, before 10 a.m. Less water evaporates, and the grass dries during the day, which helps prevent disease. Evening watering leaves grass wet overnight.