What is the soil temperature in Boulder, Colorado?

Soil temperature at 6cm in Boulder, Colorado is currently 27.0°C. Too warm to seed — the soil is heat-stressed. Wait for it to cool.

Soil temperature in Boulder, Colorado

Soil temperature

81°F27.0°C

at 6cm — germination depth

Cooling over the next 11 days.

Too warm to seed — the soil is heat-stressed. Wait for it to cool.

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 Boulder, Colorado is currently 27.0°C, and falling about 23.0°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. Too warm to seed — the soil is heat-stressed. Wait for it to cool.

8 of the next 10 days are good mowing days. The best weekend slot right now is Sunday 2pm–8pm, on the basis that temperature — 23°C.

The next recommended window in Boulder opens at 7pm on Tuesday 1 September, because anything earlier is the hour your neighbours will remember. Underfoot, the ground reads as firm after 1mm rain over the last week.

See the full mowing forecast for Boulder

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 26.4°C cooling to 0.0°C

Tuesday 1 September · 7pm–8pmConfident

7pm–8pm — heat stress — 27°C

Good:Grass wetness: Grass dryno rain since Friday
Good:Ground firmness: Ground firm1mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.95
Poor:Temperature: Heat stress27°C
Good:Wind: Wind light15 km/h
Sociable hours: A bit early or late, but finestarts when it stops being antisocial

Limiting factor:temperature

Wednesday 2 September · 8am–11amConfident

8am–11am — no rain since Friday, ground firm

Good:Grass wetness: Grass dryno rain since Friday
Good:Ground firmness: Ground firm1mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.64
Poor:Temperature: Temperature20°C
Good:Wind: Wind light11 km/h
Sociable hours: A bit early or late, but finestarts when it stops being antisocial

Limiting factor:none

Thursday 3 September · 8am–middayConfident

8am–midday — rain earlier today, ground firm

Good:Grass wetness: Grass dryrain earlier today
Good:Ground firmness: Ground firm1mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.71
Poor:Temperature: Temperature17°C
Good:Wind: Wind light13 km/h
Sociable hours: A bit early or late, but finestarts when it stops being antisocial

Limiting factor:none

Friday 4 September · 8am–11amConfident

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

Good:Grass wetness: Grass dryrain earlier today
Good:Ground firmness: Ground firm2mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.73
Poor:Temperature: Temperature18°C
Good:Wind: Wind light10 km/h
Sociable hours: A bit early or late, but finestarts when it stops being antisocial

Limiting factor:none

Saturday 5 September · 8am–10amReasonably confident

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

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm1mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.63
Poor:Temperature: Temperature20°C
Good:Wind: Wind light12 km/h
Sociable hours: A bit early or late, but finestarts when it stops being antisocial

Limiting factor:none

Sunday 6 September · 2pm–8pmReasonably confident

2pm–8pm — temperature — 23°C

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm1mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.73
Marginal:Temperature: Temperature21°C
Good:Wind: Wind light11 km/h
Sociable hours: Fine by the neighbours

Limiting factor:temperature

Monday 7 September · 10am–middayReasonably confident

10am–midday — cool — 25°C

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm1mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.80
Marginal:Temperature: Temperature21°C
Good:Wind: Wind light2 km/h
Sociable hours: Fine by the neighboursstarts when it stops being antisocial

Limiting factor:temperature

Tuesday 8 September · 8am–11amReasonably confident

8am–11am — no rain since Thursday, ground firm

Good:Grass wetness: Grass dryno rain since Thursday
Good:Ground firmness: Ground firm1mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.74
Poor:Temperature: Temperature20°C
Good:Wind: Wind light8 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 dryrain earlier today
Good:Ground firmness: Ground firm1mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.86
Marginal:Temperature: Temperature17°C
Good:Wind: Wind light4 km/h

Limiting factor:none

Thursday 10 SeptemberLow confidence this far out

No — ground frozen.

Good:Grass wetness: Grass drydried off since a shower 0 hours ago
Good:Ground firmness: Ground firm2mm rain over the last week
Good:Growth: Growing wellgrowth potential 0.93
Good:Temperature: Temperature17°C
Good:Wind: Wind light2 km/h

Limiting factor:none

Nearby

Your own postcode

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