Soil temperature in Portsmouth, Virginia
Soil temperature
87°F30.7°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.
| 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 Portsmouth, Virginia is currently 30.7°C, and falling about 28.7°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.
7 of the next 10 days are good mowing days. The best weekend slot right now is Sunday 10am–8pm, on the basis that no rain since Saturday, ground firm.
The next recommended window in Portsmouth opens at 8am on Wednesday 2 September, because anything earlier is the hour your neighbours will remember. Underfoot, the ground reads as firm after 2mm rain over the last week.
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 29.3°C cooling to 0.0°C
Tuesday 1 September: Not worth it. No — heat stress, 30°C.
Tuesday 1 SeptemberConfident
No — heat stress, 30°C.
- Good:Grass wetness
- Grass dryno rain since Monday
- Good:Ground firmness
- Ground firm2mm rain over the last week
- Marginal:Growth
- Growing slowlygrowth potential 0.35
- Poor:Temperature
- Heat stress28°C
- Good:Wind
- Wind light6 km/h
Limiting factor:temperature
Wednesday 2 September: Good. 8am–9am — growing slowly — growth potential 0.23
Wednesday 2 September · 8am–9amConfident
8am–9am — growing slowly — growth potential 0.23
- Good:Grass wetness
- Grass dryno rain since Monday
- Good:Ground firmness
- Ground firm2mm rain over the last week
- Marginal:Growth
- Growing slowlygrowth potential 0.23
- Poor:Temperature
- Cool25°C
- Good:Wind
- Wind light9 km/h
- Sociable hours
- A bit early or late, but finestarts when it stops being antisocial
Limiting factor:growth
Thursday 3 September: Good. 8am–9am — barely growing — growth potential 0.17
Thursday 3 September · 8am–9amConfident
8am–9am — barely growing — growth potential 0.17
- Good:Grass wetness
- Grass dryno rain since Monday
- Good:Ground firmness
- Ground firm2mm rain over the last week
- Poor:Growth
- Barely growinggrowth potential 0.17
- Poor:Temperature
- Cool24°C
- Good:Wind
- Wind light6 km/h
- Sociable hours
- A bit early or late, but finestarts once the dew has burnt off
Limiting factor:growth
Friday 4 September: Good. 8am–10am — growing slowly — growth potential 0.21
Friday 4 September · 8am–10amConfident
8am–10am — growing slowly — growth potential 0.21
- Good:Grass wetness
- Grass dryrain earlier today
- Good:Ground firmness
- Ground firm2mm rain over the last week
- Poor:Growth
- Growing slowlygrowth potential 0.21
- Poor:Temperature
- Cool24°C
- Good:Wind
- Wind light7 km/h
- Sociable hours
- A bit early or late, but finestarts when it stops being antisocial
Limiting factor:growth
Saturday 5 September: Good. 8am–8pm — cool — 24°C
Saturday 5 September · 8am–8pmReasonably confident
8am–8pm — cool — 24°C
- Good:Grass wetness
- Grass dryrain earlier today
- Good:Ground firmness
- Ground firm6mm rain over the last week
- Good:Growth
- Growing steadilygrowth potential 0.48
- Marginal:Temperature
- Cool24°C
- Good:Wind
- Wind light18 km/h
- Sociable hours
- A bit early or late, but finestarts when it stops being antisocial
Limiting factor:temperature
Sunday 6 September: Good. 10am–8pm — no rain since Saturday, ground firm
Sunday 6 September · 10am–8pmReasonably confident
10am–8pm — no rain since Saturday, ground firm
- Good:Grass wetness
- Grass dryno rain since Saturday
- Good:Ground firmness
- Ground firm6mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.75
- Good:Temperature
- Temperature22°C
- Good:Wind
- Wind light17 km/h
- Sociable hours
- Fine by the neighboursstarts when it stops being antisocial
Limiting factor:none
Monday 7 September: Good. 10am–8pm — cool — 24°C
Monday 7 September · 10am–8pmReasonably confident
10am–8pm — cool — 24°C
- Good:Grass wetness
- Grass dryno rain since Saturday
- Good:Ground firmness
- Ground firm6mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.82
- Marginal:Temperature
- Temperature20°C
- Good:Wind
- Wind light4 km/h
- Sociable hours
- Fine by the neighboursstarts when it stops being antisocial
Limiting factor:temperature
Tuesday 8 September: Good. 8am–midday — no rain since Saturday, ground firm
Tuesday 8 September · 8am–middayReasonably confident
8am–midday — 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 0.72
- Poor:Temperature
- Temperature20°C
- Good:Wind
- Wind light7 km/h
- Sociable hours
- A bit early or late, but finestarts when it stops being antisocial
Limiting factor:none
Wednesday 9 September: Not worth it. No — ground frozen.
Wednesday 9 SeptemberLow confidence this far out
No — ground frozen.
- Marginal:Grass wetness
- Grass dryno rain since Saturday
- Good:Ground firmness
- Ground firm4mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.79
- Good:Temperature
- Temperature22°C
- Good:Wind
- Wind light9 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 firm5mm rain over the last week
- Good:Growth
- Growing steadilygrowth potential 0.36
- Poor:Temperature
- Cool24°C
- Good:Wind
- Wind light17 km/h
Limiting factor:growth
Nearby
Your own postcode
These are town-centre figures. Yours will differ a little.