Boise
Treat broadleaf49°F→ steady
Fall is the best time to treat dandelions and clover: they pull weed killer down to their roots.
Broadleaf window Sep 11 – Oct 25
Idaho Weed Watch · updated Nov 3, 1:18 AM CT
When to apply pre-emergent in Idaho
Live soil temperatures for Boise, Idaho Falls and Coeur d'Alene, updated every three hours. Weeds sprout by soil temperature, not by the calendar, so the right week moves from year to year.
In Idaho, 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 Apr 11 – May 17
Stops crabgrass and other summer weeds before they sprout.
Fall: no pre-emergentThis season
Treat broadleaf weeds Sep 1 – Oct 25
Fall is seeding season here, and pre-emergent would stop grass seed too.
Right now · fall (seeding season)
Treat broadleaf weeds now: Boise. Broadleaf season over: Idaho Falls and Coeur d'Alene
Soil is 43–49°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.
Idaho Falls
Done for now44°F↓ cooling
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Oct 4
Coeur d'Alene
Done for now43°F→ steady
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Oct 19
Idaho 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 Idaho 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) |
|---|---|---|
| Boise | Apr 11 – Apr 28 | None (seeding season) · treat broadleaf Sep 11 – Oct 25 |
| Idaho Falls | May 3 – May 17 | None (seeding season) · treat broadleaf Sep 1 – Oct 4 |
| Coeur d'Alene | Apr 30 – May 14 | 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 Idaho are identifying
We record the state each identification comes from. Idaho'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 Idaho this fall
Questions about Idaho
When should I apply crabgrass pre-emergent in Idaho?
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 Apr 11 – Apr 28 in Boise; May 3 – May 17 in Idaho Falls; Apr 30 – May 14 in Coeur d'Alene.
Should I put down pre-emergent in the fall in Idaho?
Usually not. Fall is the best time to seed a cool-season lawn in Idaho, 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 Idaho right now?
As of Nov 3, 1:18 AM CT: Boise 49°F, Idaho Falls 44°F, Coeur d'Alene 43°F (5-day average, about 2.4 inches down). Treat broadleaf weeds now: Boise. Broadleaf season over: Idaho Falls and Coeur d'Alene.
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.