About LawnWeather
LawnWeather tells you when to put down crabgrass preventer, fertilize and seed your lawn, based on this year's weather where you live instead of a fixed date on the calendar.
Why soil temperature
Grass and weeds respond to soil temperature, not the calendar. Crabgrass sprouts once the soil 4 inches down stays above 55°F, so preventer has to be down before then. Warm-season grasses like Bermuda and zoysia grow in earnest above 65°F. Spring comes at a different time every year, and the right week moves with it.
Where the data comes from
- Daily high and low temperatures since 2016 for your location, from thePRISM Climate Group at Oregon State University (4 km daily grids), served by NOAA's Regional Climate Centers.
- The current forecast from the National Weather Service.
- ZIP code locations from the U.S. Census Bureau.
How the timing is calculated
We estimate the soil temperature 4 inches down from a 5-day running average of daily air temperature, which tracks soil under turf reasonably well. It is an estimate, not a measurement: sun, shade, slope, soil type and moisture can make your yard a few degrees warmer or cooler.
A soil temperature window opens once the estimate has held past its threshold for 5 days in a row, so a warm spell in January doesn't start spring early:
- Crabgrass preventer: when soil reaches 50°F, before it stays above 55°F.
- Spring fertilizer for cool-season grass: soil above 55°F.
- Fall fertilizer for cool-season grass: from when soil drops below 70°F until it cools to about 45°F.
- Feeding and seeding warm-season grass: soil above 65°F.
- Fall pre-emergent for warm-season lawns: as soil drops below 70°F.
Cool-season grass seeding is timed from the first fall frost instead: about 75 to 25 days before it, so seedlings can establish. Frost means a low of 32°F or colder, and the typical dates on the state and city pages are medians for 2016–2025.
Use it as a guide
LawnWeather is a planning tool, not a replacement for the product label. Always follow the label, and for advice on your specific lawn, your state's Cooperative Extension Service is an excellent free resource.
Who runs LawnWeather
LawnWeather is an independent website. If a date looks wrong for your area, please let us know.