Great Falls, MT Lawn Care Calendar
In a typical year, put down crabgrass preventer in Great Falls between May 4 and Jun 5. The best time to overseed is between Jul 26 and Sep 14. The last spring frost usually comes around May 6. Most lawns here are cool-season grass (tall fescue, Kentucky bluegrass, ryegrass).
Typical lawn care dates in Great Falls
| Task | Typical window |
|---|---|
| Crabgrass preventer (pre-emergent)Crabgrass sprouts once soil stays above 55°F. Apply when soil reaches 50°F, before that happens. | May 4 – Jun 5 |
| Spring fertilizerA light feeding once soil warms past 55°F and the grass is actively growing. | May 29 – Jul 3 |
| Overseeding & seedingLate summer to early fall: seedlings need about 6–10 weeks of growth before the first frost. | Jul 26 – Sep 14 |
| Fall fertilizerThe most important feeding for cool-season grass, from early fall until soil cools to about 45°F. | Jul 29 – Oct 17 |
Median dates, 2016–2025, from NOAA weather data for Great Falls. This year's dates can differ by a few weeks.
Month-by-month lawn care in Great Falls
- JanuaryNo treatments due; mow as needed.
- FebruaryNo treatments due; mow as needed.
- MarchNo treatments due; mow as needed.
- AprilNo treatments due; mow as needed.
- MayCrabgrass preventer (pre-emergent)Spring fertilizer
- JuneCrabgrass preventer (pre-emergent)Spring fertilizer
- JulySpring fertilizerOverseeding & seedingFall fertilizer
- AugustOverseeding & seedingFall fertilizer
- SeptemberOverseeding & seedingFall fertilizer
- OctoberFall fertilizer
- NovemberNo treatments due; mow as needed.
- DecemberNo treatments due; mow as needed.
Soil temperature in Great Falls by month
Average soil temperature 4 inches down, estimated from 2016–2025 weather. It bottoms out in February at 23°F and peaks in July at 70°F. Crabgrass preventer goes down when it reaches 50°F, usually around May 4.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 26°F | 23°F | 33°F | 42°F | 53°F | 62°F | 70°F | 69°F | 61°F | 47°F | 37°F | 29°F |
Great Falls lawn timing, year by year
Over the last 10 years, soil in Great Falls reached 50°F, the signal for crabgrass preventer, as early as Apr 27 (2020) and as late as May 13 (2019): 16 days apart. A fixed calendar date can't follow that, which is why the report above uses this year's soil temperature. Between the typical last spring frost (May 6) and first fall frost (Oct 9), the growing season lasts about 156 days.
| Year | Crabgrass window opened | Last spring frost | First fall frost |
|---|---|---|---|
| 2025 | Apr 30 | May 6 | Oct 6 |
| 2024 | May 12 | May 5 | Oct 19 |
| 2023 | Apr 30 | Apr 24 | Oct 24 |
| 2022 | May 4 | May 21 | Oct 23 |
| 2021 | Apr 30 | May 23 | Oct 12 |
| 2020 | Apr 27 | May 13 | Oct 15 |
| 2019 | May 13 | May 19 | Sep 29 |
| 2018 | May 4 | Apr 26 | Sep 30 |
| 2017 | May 5 | May 3 | Sep 24 |
| 2016 | May 4 | May 1 | Sep 13 |
Estimated from daily temperatures for Great Falls. A dash means it didn't happen that year.
Frequently asked questions
When should I apply pre-emergent in Great Falls?
In a typical year, between May 4 and Jun 5. Put it down when soil reaches 50°F, before it stays above 55°F and crabgrass starts sprouting. Early springs move this up by a week or more, so check this year's soil temperature above.
When is the best time to plant grass seed in Great Falls?
Early fall, typically Jul 26 – Sep 14, while soil cools from 65°F toward 50°F.
When is the last frost in Great Falls?
The median last spring frost is May 6 and the median first fall frost is Oct 9 (2016–2025).
How long is the growing season in Great Falls?
About 156 days, from the median last spring frost on May 6 to the median first fall frost on Oct 9 (2016–2025).
Lawn care guides
More Montana lawn calendars
Nearby cities in other states
- Coeur d'Alene, ID 256 miles away · crabgrass preventer Apr 27 – May 18
- Sheridan, WY 279 miles away · crabgrass preventer May 8 – Jun 1
- Idaho Falls, ID 279 miles away · crabgrass preventer May 3 – Jun 6
- Spokane, WA 286 miles away · crabgrass preventer Apr 26 – May 15