Portland, Oregon
Mowing
When you can next cut it, and the best slot this weekend.
Best weekend slot
Sunday 10am–8pm
Verdict: Good
no rain since Thursday, ground firm
Next mow
Tomorrow 2pm–3pm
Verdict: Good
rain 4 hours ago, ground firm
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 17.4°C cooling to 0.0°C
Wednesday 2 September: Marginal. No — 1.1mm of rain falling.
Wednesday 2 SeptemberConfident
No — 1.1mm of rain falling.
- Poor:Grass wetness
- Grass wetraining now
- Good:Ground firmness
- Ground firm0mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.81
- Good:Temperature
- Temperature16°C
- Good:Wind
- Wind light11 km/h
Limiting factor:grass wetness
Thursday 3 September: Good. 2pm–3pm — rain 4 hours ago, ground firm
Thursday 3 September · 2pm–3pmConfident
2pm–3pm — rain 4 hours ago, ground firm
- Poor:Grass wetness
- Grass dryrain 4 hours ago
- Good:Ground firmness
- Ground firm4mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.55
- Good:Temperature
- Temperature12°C
- Good:Wind
- Wind light7 km/h
- Sociable hours
- Fine by the neighboursstarts once the dew has burnt off
Limiting factor:none
Friday 4 September: Good. 3pm–8pm — rain earlier today, ground soft in places
Friday 4 September · 3pm–8pmConfident
3pm–8pm — rain earlier today, ground soft in places
- Poor:Grass wetness
- Grass dryrain earlier today
- Good:Ground firmness
- Ground soft in places17mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.56
- Good:Temperature
- Temperature12°C
- Good:Wind
- Wind light7 km/h
- Sociable hours
- Fine by the neighboursstarts once the dew has burnt off
Limiting factor:none
Saturday 5 September: Good. 8am–8pm — no rain since Thursday, ground firm
Saturday 5 September · 8am–8pmConfident
8am–8pm — no rain since Thursday, ground firm
- Good:Grass wetness
- Grass dryno rain since Thursday
- Good:Ground firmness
- Ground firm32mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.88
- Good:Temperature
- Temperature12°C
- Good:Wind
- Wind light3 km/h
- Sociable hours
- A bit early or late, but finestarts when it stops being antisocial
Limiting factor:none
Sunday 6 September: Good. 10am–8pm — no rain since Thursday, ground firm
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 firm32mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.98
- Good:Temperature
- Temperature14°C
- Good:Wind
- Wind light4 km/h
- Sociable hours
- Fine by the neighboursstarts when it stops being antisocial
Limiting factor:none
Monday 7 September: Good. 10am–8pm — no rain since Thursday, ground firm
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 firm32mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 1.00
- Good:Temperature
- Temperature14°C
- Good:Wind
- Wind light3 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 Thursday, ground firm
Tuesday 8 September · 8am–8pmReasonably confident
8am–8pm — no rain since Thursday, ground firm
- Good:Grass wetness
- Grass dryno rain since Thursday
- Good:Ground firmness
- Ground firm32mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.99
- Good:Temperature
- Temperature15°C
- Good:Wind
- Wind light4 km/h
- Sociable hours
- A bit early or late, but finestarts when it stops being antisocial
Limiting factor:none
Wednesday 9 September: Good. 8am–6pm — no rain since Thursday, ground firm
Wednesday 9 September · 8am–6pmReasonably confident
8am–6pm — no rain since Thursday, ground firm
- Good:Grass wetness
- Grass dryno rain since Thursday
- Good:Ground firmness
- Ground firm32mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.97
- Good:Temperature
- Temperature15°C
- Good:Wind
- Wind light4 km/h
- Sociable hours
- A bit early or late, but finestarts when it stops being antisocial
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 dryno rain since Thursday
- Good:Ground firmness
- Ground firm28mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.98
- Marginal:Temperature
- Temperature15°C
- Good:Wind
- Wind light2 km/h
Limiting factor:none
Friday 11 September: Not worth it. No — ground frozen.
Friday 11 SeptemberLow confidence this far out
No — ground frozen.
- Good:Grass wetness
- Grass dryno rain in over a week
- Good:Ground firmness
- Ground firm15mm rain over the last week
- Good:Growth
- Growing wellgrowth potential 0.97
- Good:Temperature
- Temperature16°C
- Good:Wind
- Wind light5 km/h
Limiting factor:none
Growth
How fast it is growing, and when it will need cutting again.
0.81Growing strongly
Growth potential, 0 to 1 — the turf-industry measure of how fast grass can grow at today's temperature and day length.
Putting on about 4.8mm a day. A lawn cut today would be ready for another in around 4 days.
Worked out from the PACE Turf growth potential model and day length —how and why.
What this means right now
Good: Seeding window open
Seeding conditions are open — soil is 17.4°C at 6cm and holding above 12.5°C.
Warning: Heat stress
Sunday 6 September gets hot enough to stress the sward. Mow early or late, and raise the height.
Seeding
Soil temperature at germination depth, and when the window opens.
Soil temperature
63°F17.4°C
at 6cm — germination depth
Cooling over the next 10 days.
Seeding conditions are open — soil is 17.4°C at 6cm and holding above 12.5°C.
Cross-checks against an independent estimate from air temperature (17.5°C), which agrees to within 0.1°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.
| 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 |
Feeding
Why timing decides whether a feed does anything at all.
Coming in the app
Grass takes up nitrogen when it is growing. Feed a lawn that has stopped and most of it washes past the roots — which is why timing beats product choice.
Right now this lawn is growing well enough to use a feed.
The app will work out the actual feeding windows for your lawn — along with weed control, scarifying and moss treatment — and tell you when they open without you having to check.
Portland, Oregon in detail
Soil temperature at 6cm in Portland, Oregon is currently 17.4°C, and falling about 17.4°C over the next 10 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 17.4°C at 6cm and holding above 12.5°C.
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 Thursday, ground firm.
The next recommended window in Portland opens at 2pm on Thursday 3 September, because that is when the dew has burnt off — earlier than that and you are cutting wet grass. Underfoot, the ground reads as firm after 0mm rain over the last week.
Forecast from Open-Meteo, refreshed hourly. Soil temperature is modelled, not measured — how that works and where the thresholds come from.