Cheyenne
Treat broadleaf48°F↓ cooling
Fall is the best time to treat dandelions and clover: they pull weed killer down to their roots.
Broadleaf window Sep 1 – Oct 16
Wyoming Weed Watch · updated Nov 3, 1:18 AM CT
When to apply pre-emergent in Wyoming
Live soil temperatures for Cheyenne, Casper and Sheridan, updated every three hours. Weeds sprout by soil temperature, not by the calendar, so the right week moves from year to year.
In Wyoming, 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 May 1 – May 22
Stops crabgrass and other summer weeds before they sprout.
Fall: no pre-emergentThis season
Treat broadleaf weeds Sep 1 – Oct 18
Fall is seeding season here, and pre-emergent would stop grass seed too.
Right now · fall (seeding season)
Treat broadleaf weeds now: Cheyenne and Casper. Broadleaf season over: Sheridan
Soil is 41–48°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.
Casper
Treat broadleaf46°F↓ cooling
Fall is the best time to treat dandelions and clover: they pull weed killer down to their roots.
Broadleaf window Sep 1 – Oct 17
Sheridan
Done for now41°F→ steady
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Oct 18
Wyoming 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 Wyoming 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) |
|---|---|---|
| Cheyenne | May 12 – May 21 | None (seeding season) · treat broadleaf Sep 1 – Oct 16 |
| Casper | May 1 – May 19 | None (seeding season) · treat broadleaf Sep 1 – Oct 17 |
| Sheridan | May 9 – May 22 | None (seeding season) · treat broadleaf Sep 1 – Oct 18 |
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 Wyoming are identifying
We record the state each identification comes from. Wyoming'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 Wyoming this fall
Questions about Wyoming
When should I apply crabgrass pre-emergent in Wyoming?
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 May 12 – May 21 in Cheyenne; May 1 – May 19 in Casper; May 9 – May 22 in Sheridan.
Should I put down pre-emergent in the fall in Wyoming?
Usually not. Fall is the best time to seed a cool-season lawn in Wyoming, 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 Wyoming right now?
As of Nov 3, 1:18 AM CT: Cheyenne 48°F, Casper 46°F, Sheridan 41°F (5-day average, about 2.4 inches down). Treat broadleaf weeds now: Cheyenne and Casper. Broadleaf season over: Sheridan.
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.