Seattle, WA Lawn Care Calendar
In a typical year, put down crabgrass preventer in Seattle between Apr 5 and May 14. The best time to overseed is between Sep 1 and Oct 21. The last spring frost usually comes around Mar 12. Most lawns here are cool-season grass (tall fescue, Kentucky bluegrass, ryegrass).
Typical lawn care dates in Seattle
| Task | Typical window |
|---|---|
| Crabgrass preventer (pre-emergent)Crabgrass sprouts once soil stays above 55°F. Apply when soil reaches 50°F, before that happens. | Apr 5 – May 14 |
| Spring fertilizerA light feeding once soil warms past 55°F and the grass is actively growing. | May 7 – Jun 11 |
| Overseeding & seedingLate summer to early fall: seedlings need about 6–10 weeks of growth before the first frost. | Sep 1 – Oct 21 |
| Fall fertilizerThe most important feeding for cool-season grass, from early fall until soil cools to about 45°F. | Jul 16 – Nov 13 |
Median dates, 2016–2025, from NOAA weather data for Seattle. This year's dates can differ by a few weeks.
Month-by-month lawn care in Seattle
- JanuaryNo treatments due; mow as needed.
- FebruaryNo treatments due; mow as needed.
- MarchNo treatments due; mow as needed.
- AprilCrabgrass preventer (pre-emergent)
- MayCrabgrass preventer (pre-emergent)Spring fertilizer
- JuneSpring fertilizer
- JulyFall fertilizer
- AugustFall fertilizer
- SeptemberOverseeding & seedingFall fertilizer
- OctoberOverseeding & seedingFall fertilizer
- NovemberFall fertilizer
- DecemberNo treatments due; mow as needed.
Soil temperature in Seattle by month
Average soil temperature 4 inches down, estimated from 2016–2025 weather. It bottoms out in January at 42°F and peaks in August at 68°F. Crabgrass preventer goes down when it reaches 50°F, usually around Apr 5.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 42°F | 42°F | 45°F | 50°F | 57°F | 61°F | 67°F | 68°F | 63°F | 54°F | 47°F | 42°F |
Seattle lawn timing, year by year
Over the last 10 years, soil in Seattle reached 50°F, the signal for crabgrass preventer, as early as Jan 29 (2024) and as late as Apr 26 (2023): 87 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 (Mar 12) and first fall frost (Nov 15), the growing season lasts about 248 days.
| Year | Crabgrass window opened | Last spring frost | First fall frost |
|---|---|---|---|
| 2025 | Mar 26 | Feb 14 | Dec 28 |
| 2024 | Jan 29 | Mar 8 | Dec 4 |
| 2023 | Apr 26 | Mar 13 | Oct 29 |
| 2022 | Mar 27 | Mar 11 | Nov 10 |
| 2021 | Apr 16 | Mar 17 | Dec 26 |
| 2020 | Apr 16 | Mar 19 | Nov 9 |
| 2019 | Mar 19 | Mar 12 | Oct 30 |
| 2018 | Apr 7 | Mar 25 | Nov 19 |
| 2017 | Apr 18 | Feb 26 | Nov 4 |
| 2016 | Apr 1 | Jan 9 | Dec 7 |
Estimated from daily temperatures for Seattle. A dash means it didn't happen that year.
Frequently asked questions
When should I apply pre-emergent in Seattle?
In a typical year, between Apr 5 and May 14. 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 Seattle?
Early fall, typically Sep 1 – Oct 21, while soil cools from 65°F toward 50°F.
When is the last frost in Seattle?
The median last spring frost is Mar 12 and the median first fall frost is Nov 15 (2016–2025).
How long is the growing season in Seattle?
About 248 days, from the median last spring frost on Mar 12 to the median first fall frost on Nov 15 (2016–2025).
Lawn care guides
More Washington lawn calendars
Nearby cities in other states
- Portland, OR 145 miles away · crabgrass preventer Apr 1 – May 5
- Salem, OR 188 miles away · crabgrass preventer Apr 1 – May 9
- Eugene, OR 249 miles away · crabgrass preventer Apr 5 – May 13
- Bend, OR 250 miles away · crabgrass preventer May 7 – Jun 4