Billings
Done for now42°F→ steady
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Oct 22
Montana Weed Watch · updated Nov 3, 1:18 AM CT
When to apply pre-emergent in Montana
Live soil temperatures for Billings, Missoula, Great Falls and Bozeman, updated every three hours. Weeds sprout by soil temperature, not by the calendar, so the right week moves from year to year.
In Montana, 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 29 – May 17
Stops crabgrass and other summer weeds before they sprout.
Fall: no pre-emergentThis season
Treat broadleaf weeds Sep 1 – Oct 22
Fall is seeding season here, and pre-emergent would stop grass seed too.
Right now · fall (seeding season)
Broadleaf season over across Montana
Soil is 40–42°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.
Missoula
Done for now40°F↓ cooling
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Oct 12
Great Falls
Done for now40°F↑ warming
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Oct 20
Bozeman
Done for now40°F→ steady
Done for this year. Spot-treat on a mild day, or wait for spring.
Broadleaf window Sep 1 – Sep 30
Montana 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 Montana 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) |
|---|---|---|
| Billings | Apr 29 – May 7 | None (seeding season) · treat broadleaf Sep 1 – Oct 22 |
| Missoula | May 3 – May 14 | None (seeding season) · treat broadleaf Sep 1 – Oct 12 |
| Great Falls | May 2 – May 15 | None (seeding season) · treat broadleaf Sep 1 – Oct 20 |
| Bozeman | May 4 – May 17 | None (seeding season) · treat broadleaf Sep 1 – Sep 30 |
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 Montana are identifying
We record the state each identification comes from. Montana'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 Montana this fall
Questions about Montana
When should I apply crabgrass pre-emergent in Montana?
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 29 – May 7 in Billings; May 3 – May 14 in Missoula; May 2 – May 15 in Great Falls; May 4 – May 17 in Bozeman.
Should I put down pre-emergent in the fall in Montana?
Usually not. Fall is the best time to seed a cool-season lawn in Montana, 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 Montana right now?
As of Nov 3, 1:18 AM CT: Billings 42°F, Missoula 40°F, Great Falls 40°F, Bozeman 40°F (5-day average, about 2.4 inches down). Broadleaf season over across Montana.
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.