What is the soil temperature in Seattle, Washington?

Soil temperature at 6cm in Seattle, Washington is currently 20.2°C. Seeding conditions are open — soil is 20.2°C at 6cm and holding above 12.5°C.

Soil temperature in Seattle, Washington

Soil temperature

68°F20.2°C

at 6cm — germination depth

Cooling over the next 11 days.

Seeding conditions are open — soil is 20.2°C at 6cm and holding above 12.5°C.

Most cool-season lawns in the northern US and Canada are bluegrass, tall fescue, or a mix of the two. We assume that, and use12.5°C as the seeding threshold.

I know what grass I have

The differences are small. Ryegrass is the quickest off the mark; bluegrass is the slowest and wants the warmest soil. Everything else sits between.

Soil temperature at 6cm for reliable germination. Sources onthe method page.
Species	Soil temp	Days
Perennial ryegrass	8°C	5–10
Red / chewings fescue	8–10°C	10–14
Tall fescuelikely yours	10–12°C	10–14
Browntop bentColonial bentgrass	10–12°C	14–21
Smooth-stalked meadow grassKentucky bluegrasslikely yours	12–13°C	14–28

Soil temperature at 6cm in Seattle, Washington is currently 20.2°C, and falling about 17.0°C over the next 11 days. That depth matters because it is where grass seed sits and where roots start working, and it lags air temperature by days — which is why a warm afternoon here tells you very little on its own.

Lawns in this area are typically Kentucky bluegrass with tall fescue, the usual mix for cool-season lawns at this latitude. That blend needs the soil to hold above 12.5°C before seed germinates reliably. Seeding conditions are open — soil is 20.2°C at 6cm and holding above 12.5°C.

8 of the next 10 days are good mowing days. The best weekend slot right now is Saturday 8am–8pm, on the basis that no rain since Thursday, ground firm.

The next recommended window in Seattle opens at 5pm on Tuesday 1 September, and holds while conditions stay put. Underfoot, the ground reads as firm after 4mm rain over the last week.

See the full mowing forecast for Seattle

The next 10 days

Column height is how mowable the day is; the lighter band is the best stretch within it. The line is soil temperature at 6cm. It crosses the seeding threshold inside this forecast.

12.5°C — seeding

Soil at 6cm 19.6°C cooling to 0.0°C

Tuesday 1 September · 5pm–8pmConfident

5pm–8pm — no rain since Saturday, ground firm

Good:Grass wetness: Grass dryno rain since Saturday
Good:Ground firmness: Ground firm4mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.82
Good:Temperature: Temperature19°C
Good:Wind: Wind light14 km/h
Sociable hours: A bit early or late, but fine

Limiting factor:none

Wednesday 2 September · 2pm–5pmConfident

2pm–5pm — dried off since a shower 1 hour ago, ground firm

Good:Grass wetness: Grass dryno rain since Saturday
Good:Ground firmness: Ground firm4mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.74
Good:Temperature: Temperature13°C
Good:Wind: Wind light9 km/h
Sociable hours: Fine by the neighboursstarts once the rain has passed

Limiting factor:none

Thursday 3 September · midday–5pmConfident

midday–5pm — rain earlier today, ground firm

Marginal:Grass wetness: Grass dryrain earlier today
Good:Ground firmness: Ground firm4mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.51
Good:Temperature: Temperature11°C
Good:Wind: Wind light14 km/h
Sociable hours: Fine by the neighboursstarts once the dew has burnt off

Limiting factor:none

Friday 4 September · 11am–8pmConfident

11am–8pm — rain earlier today, ground firm

Good:Grass wetness: Grass dryrain earlier today
Good:Ground firmness: Ground firm8mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.62
Good:Temperature: Temperature10°C
Good:Wind: Wind light3 km/h
Sociable hours: Fine by the neighboursstarts once the dew has burnt off

Limiting factor:none

Saturday 5 September · 8am–8pmReasonably confident

8am–8pm — no rain since Thursday, ground firm

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm9mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.73
Good:Temperature: Temperature10°C
Good:Wind: Wind light5 km/h
Sociable hours: A bit early or late, but finestarts once the dew has burnt off

Limiting factor:none

Sunday 6 September · 10am–8pmReasonably confident

10am–8pm — no rain since Thursday, ground firm

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm6mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.89
Good:Temperature: Temperature12°C
Good:Wind: Wind light1 km/h
Sociable hours: Fine by the neighboursstarts when it stops being antisocial

Limiting factor:none

Monday 7 September · 10am–8pmReasonably confident

10am–8pm — no rain since Thursday, ground firm

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm6mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.98
Good:Temperature: Temperature14°C
Good:Wind: Wind light1 km/h
Sociable hours: Fine by the neighboursstarts when it stops being antisocial

Limiting factor:none

Tuesday 8 September · 8am–6pmReasonably confident

8am–6pm — no rain since Thursday, ground firm

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm6mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.91
Good:Temperature: Temperature15°C
Good:Wind: Wind light10 km/h
Sociable hours: A bit early or late, but finestarts when it stops being antisocial

Limiting factor:none

Wednesday 9 SeptemberLow confidence this far out

No — ground frozen.

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm6mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.72
Good:Temperature: Temperature12°C
Good:Wind: Wind light6 km/h

Limiting factor:none

Thursday 10 SeptemberLow confidence this far out

No — ground frozen.

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm5mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.94
Marginal:Temperature: Temperature13°C
Good:Wind: Wind light2 km/h

Limiting factor:none

Nearby

Your own postcode

These are town-centre figures. Yours will differ a little.