Denver
Treat broadleaf51°F↓ cooling
Fall is the best time to treat dandelions and clover: they pull weed killer down to their roots.
Broadleaf window Sep 13 – Oct 28
Colorado Weed Watch · updated Nov 3, 1:18 AM CT
When to apply pre-emergent in Colorado
Live soil temperatures for Denver, Colorado Springs, Fort Collins and Grand Junction, updated every three hours. Weeds sprout by soil temperature, not by the calendar, so the right week moves from year to year.
In Colorado, 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 6 – May 30
Stops crabgrass and other summer weeds before they sprout.
Fall: no pre-emergentThis season
Treat broadleaf weeds Sep 9 – Oct 28
Fall is seeding season here, and pre-emergent would stop grass seed too.
Right now · fall (seeding season)
Treat broadleaf weeds now across Colorado
Soil is 50–51°F now. In fall, dandelions, clover and creeping Charlie pull sugars — and weed killer — down to their roots. Seeding this fall? Skip pre-emergent; it stops grass seed too.
Soil temperature by city
Soil 2 inches down, 5-day average: solid line = the last two weeks, dashed = the six-day forecast.
Colorado Springs
Treat broadleaf50°F↓ cooling
Fall is the best time to treat dandelions and clover: they pull weed killer down to their roots.
Broadleaf window Sep 9 – Oct 27
Fort Collins
Treat broadleaf50°F↓ cooling
Fall is the best time to treat dandelions and clover: they pull weed killer down to their roots.
Broadleaf window Sep 13 – Oct 28
Grand Junction
Treat broadleaf51°F↓ cooling
Fall is the best time to treat dandelions and clover: they pull weed killer down to their roots.
Broadleaf window Sep 13 – Oct 27
Colorado 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 Colorado 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) |
|---|---|---|
| Denver | Apr 23 – May 7 | None (seeding season) · treat broadleaf Sep 13 – Oct 28 |
| Colorado Springs | May 13 – May 30 | None (seeding season) · treat broadleaf Sep 9 – Oct 27 |
| Fort Collins | Apr 30 – May 13 | None (seeding season) · treat broadleaf Sep 13 – Oct 28 |
| Grand Junction | Apr 6 – Apr 23 | None (seeding season) · treat broadleaf Sep 13 – Oct 27 |
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 Colorado are identifying
We record the state each identification comes from. Colorado'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 Colorado this fall
Questions about Colorado
When should I apply crabgrass pre-emergent in Colorado?
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 23 – May 7 in Denver; May 13 – May 30 in Colorado Springs; Apr 30 – May 13 in Fort Collins; Apr 6 – Apr 23 in Grand Junction.
Should I put down pre-emergent in the fall in Colorado?
Usually not. Fall is the best time to seed a cool-season lawn in Colorado, 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 Colorado right now?
As of Nov 3, 1:18 AM CT: Denver 51°F, Colorado Springs 50°F, Fort Collins 50°F, Grand Junction 51°F (5-day average, about 2.4 inches down). Treat broadleaf weeds now across Colorado.
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.