Best days to apply pre-emergent, by city
Crabgrass pre-emergent: before soil holds 55°F (about 200 GDD), then water it in. Pick a city for a live 7-day verdict from the National Weather Service forecast and the months that usually work there.
Alabama
Arizona
Arkansas
California
Colorado
Connecticut
District of Columbia
Florida
Georgia
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Nebraska
Nevada
New Mexico
Oklahoma
Oregon
Rhode Island
South Carolina
Virginia
Washington
Wisconsin
The rules Fairsky uses
- Soil temperature is estimated from the average air temperature over about five days (past and forecast); Fairsky labels it as an estimate.
- Spring: below about 50°F soil it's too early; roughly 50–58°F is prime time; up to 65°F is late but not lost; above that, crabgrass is already up.
- Rain helps: about a quarter to half an inch in the next three days waters it in. More than an inch in the next 24 hours means hold off, since a downpour can wash granules away. (Fairsky default)
- Fall (August–October, soil 55–70°F): a window for winter weeds like henbit, chickweed and Poa annua.
- Wind under 20 mph while spreading. (Fairsky default)
Your product's label wins.
Sources: Purdue Turf: pre-emergence timing · K-State: predicting crabgrass emergence · Iowa State: how to control crabgrass
The app covers 47 activities in all: see every activity and its rules.
Fairsky is not a substitute for official warnings. For warnings, go to weather.gov.
Live forecasts: National Weather Service / NOAA (public domain), fetched by your browser. Climate averages: NOAA NCEI U.S. Climate Normals, 1991–2020 (public domain). Activity thresholds: product data sheets, ACI and university extension guidance, linked on each page; your product’s label wins.