Soil temperature in Ann Arbor, Michigan

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.
SpeciesSoil tempDays
Perennial ryegrass8°C5–10
Red / chewings fescue8–10°C10–14
Tall fescuelikely yours10–12°C10–14
Browntop bentColonial bentgrass10–12°C14–21
Smooth-stalked meadow grassKentucky bluegrasslikely yours12–13°C14–28

Soil temperature at 6cm in Ann Arbor, Michigan is currently 27.0°C, and falling about 24.8°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 Monday 10am–8pm, on the basis that no rain since Friday, ground firm.

The next recommended window in Ann Arbor opens at 8pm on Tuesday 1 September, and holds while conditions stay put. Underfoot, the ground reads as firm after 38mm rain over the last week.

See the full mowing forecast for Ann Arbor

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 27.0°C cooling to 0.0°C

Tuesday 1 September: Good. 8pm–9pm — heat stress — 26°C

Tuesday 1 September · 8pm–9pmConfident

8pm–9pm — heat stress — 26°C

Good:Grass wetness
Grass dryno rain since Monday
Good:Ground firmness
Ground firm38mm rain over the last week
Good:Growth
Growing wellgrowth potential 0.61
Marginal:Temperature
Heat stress26°C
Good:Wind
Wind light7 km/h
Sociable hours
Your neighbours will remember it

Limiting factor:temperature

Wednesday 2 September: Good. 8am–11am — no rain since Monday, ground firm

Wednesday 2 September · 8am–11amConfident

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

Good:Grass wetness
Grass dryno rain since Monday
Good:Ground firmness
Ground firm38mm rain over the last week
Good:Growth
Growing steadilygrowth potential 0.40
Poor:Temperature
Temperature22°C
Good:Wind
Wind light11 km/h
Sociable hours
A bit early or late, but finestarts at first light

Limiting factor:none

Thursday 3 September: Good. midday–1pm — heat stress — 27°C

Thursday 3 September · midday–1pmConfident

midday–1pm — heat stress — 27°C

Good:Grass wetness
Grass dryrain earlier today
Good:Ground firmness
Ground firm8mm rain over the last week
Good:Growth
Growing wellgrowth potential 0.55
Poor:Temperature
Temperature22°C
Good:Wind
Wind light5 km/h
Sociable hours
Fine by the neighboursstarts once the dew has burnt off

Limiting factor:temperature

Friday 4 September: Good. 8am–9am — rain earlier today, ground firm

Friday 4 September · 8am–9amConfident

8am–9am — rain earlier today, ground firm

Marginal:Grass wetness
Grass dryrain earlier today
Good:Ground firmness
Ground firm11mm rain over the last week
Good:Growth
Growing wellgrowth potential 0.85
Good:Temperature
Temperature21°C
Good:Wind
Wind light10 km/h
Sociable hours
A bit early or late, but finestarts at first light

Limiting factor:none

Saturday 5 September: Good. 8am–9pm — rain earlier today, ground firm

Saturday 5 September · 8am–9pmReasonably confident

8am–9pm — rain earlier today, ground firm

Good:Grass wetness
Grass dryrain earlier today
Good:Ground firmness
Ground firm20mm rain over the last week
Good:Growth
Growing wellgrowth potential 0.98
Marginal:Temperature
Temperature16°C
Good:Wind
Wind light8 km/h
Sociable hours
A bit early or late, but finestarts at first light

Limiting factor:none

Sunday 6 September: Good. 10am–9pm — no rain since Friday, ground firm

Sunday 6 September · 10am–9pmReasonably confident

10am–9pm — no rain since Friday, ground firm

Good:Grass wetness
Grass dryno rain since Friday
Good:Ground firmness
Ground firm20mm rain over the last week
Good:Growth
Growing wellgrowth potential 0.97
Good:Temperature
Temperature15°C
Good:Wind
Wind light7 km/h
Sociable hours
Fine by the neighboursstarts once the dew has burnt off

Limiting factor:none

Monday 7 September: Good. 10am–8pm — no rain since Friday, ground firm

Monday 7 September · 10am–8pmReasonably confident

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

Good:Grass wetness
Grass dryno rain since Friday
Good:Ground firmness
Ground firm12mm rain over the last week
Good:Growth
Growing wellgrowth potential 0.98
Marginal:Temperature
Temperature16°C
Good:Wind
Wind light7 km/h
Sociable hours
Fine by the neighboursstarts when it stops being antisocial

Limiting factor:none

Tuesday 8 September: Good. 8am–8pm — no rain since Friday, ground firm

Tuesday 8 September · 8am–8pmReasonably confident

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

Good:Grass wetness
Grass dryno rain since Friday
Good:Ground firmness
Ground firm12mm rain over the last week
Good:Growth
Growing wellgrowth potential 0.90
Marginal:Temperature
Temperature18°C
Good:Wind
Wind light10 km/h
Sociable hours
A bit early or late, but finestarts at first light

Limiting factor:none

Wednesday 9 September: Not worth it. No — ground frozen.

Wednesday 9 SeptemberLow confidence this far out

No — ground frozen.

Good:Grass wetness
Grass dryno rain since Friday
Good:Ground firmness
Ground firm12mm rain over the last week
Good:Growth
Growing wellgrowth potential 0.97
Good:Temperature
Temperature17°C
Good:Wind
Wind light11 km/h

Limiting factor:none

Thursday 10 September: Not worth it. No — ground frozen.

Thursday 10 SeptemberLow confidence this far out

No — ground frozen.

Good:Grass wetness
Grass dryrain earlier today
Good:Ground firmness
Ground firm12mm rain over the last week
Good:Growth
Growing wellgrowth potential 0.94
Good:Temperature
Temperature18°C
Good:Wind
Wind light24 km/h

Limiting factor:none

Nearby

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

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