Seattle
Done for now45°F↑ warming
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Oct 21
Washington Weed Watch · updated Nov 3, 1:18 AM CT
When to apply pre-emergent in Washington
Live soil temperatures for Seattle, Vancouver, Yakima and Spokane, updated every three hours. Weeds sprout by soil temperature, not by the calendar, so the right week moves from year to year.
In Washington, pre-emergent is a spring job: it stops crabgrass. Fall is seeding season here, so fall weed control means treating broadleaf weeds instead.
Spring pre-emergentNext season
Typically Mar 17 – May 9
Stops crabgrass and other summer weeds before they sprout.
Fall: no pre-emergentThis season
Treat broadleaf weeds Sep 1 – Nov 8
Fall is seeding season here, and pre-emergent would stop grass seed too.
Right now · fall (seeding season)
Broadleaf season over: Seattle, Yakima and Spokane. Treat broadleaf weeds now: Vancouver
Soil is 42–47°F now. Spot-treat on a mild day, or wait for spring.
Soil temperature by city
Soil 2 inches down, 5-day average: solid line = the last two weeks, dashed = the six-day forecast.
Vancouver
Treat broadleaf47°F↑ warming
Fall is the best time to treat dandelions and clover: they pull weed killer down to their roots.
Broadleaf window Sep 10 – Nov 8
Yakima
Done for now42°F↑ warming
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Oct 19
Spokane
Done for now44°F→ steady
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Oct 19
Washington pre-emergent calendar
Spring pre-emergent stops crabgrass. The window runs from the typical day soil warms to 50°F to the day it holds 55°F, when crabgrass starts germinating (2016–2025). In fall Washington lawns are in seeding season, so there is no fall pre-emergent; the window shown is for treating broadleaf weeds instead, from September until two weeks after soil usually cools to 55°F.
| City | Spring pre-emergent (crabgrass) | Fall (seeding season) |
|---|---|---|
| Seattle | Mar 22 – Apr 29 | None (seeding season) · treat broadleaf Sep 1 – Oct 21 |
| Vancouver | Mar 17 – Apr 23 | None (seeding season) · treat broadleaf Sep 10 – Nov 8 |
| Yakima | Apr 8 – Apr 27 | None (seeding season) · treat broadleaf Sep 1 – Oct 19 |
| Spokane | Apr 25 – May 9 | None (seeding season) · treat broadleaf Sep 1 – Oct 19 |
These are typical-year dates (the median of 2016–2025); any one year can run a couple of weeks earlier or later, which is what the live readings above are for. For your exact yard, check soil temperature by ZIP.
What people in Washington are identifying
We record the state each identification comes from. Washington's list appears here once it has at least 40 identifications spread over 7 or more days — so no single scan stands out. Until then, see the national list, or add yours:
Identify a weed from a photoWeeds to watch in Washington this fall
Questions about Washington
When should I apply crabgrass pre-emergent in Washington?
Put crabgrass pre-emergent down as soil warms to 50°F, before it holds 55°F and crabgrass starts germinating. In a typical year (2016–2025) that window is Mar 22 – Apr 29 in Seattle; Mar 17 – Apr 23 in Vancouver; Apr 8 – Apr 27 in Yakima; Apr 25 – May 9 in Spokane.
Should I put down pre-emergent in the fall in Washington?
Usually not. Fall is the best time to seed a cool-season lawn in Washington, and pre-emergent stops grass seed as well as weeds. Fall is the time to treat broadleaf weeds such as dandelion, clover and creeping Charlie, once the summer heat breaks and while they are still growing.
What is the soil temperature in Washington right now?
As of Nov 3, 1:18 AM CT: Seattle 45°F, Vancouver 47°F, Yakima 42°F, Spokane 44°F (5-day average, about 2.4 inches down). Broadleaf season over: Seattle, Yakima and Spokane. Treat broadleaf weeds now: Vancouver.
How the readings and dates are made, and their limits: Weed Watch method. Soil data: Open-Meteo.com (CC BY 4.0); typical dates: NASA POWER.