Seattle, Washington

Seattle, Washington47.6062, -122.3321from your postcode

Mowing

When you can next cut it, and the best slot this weekend.

Best weekend slot

Nothing doing

Verdict: Not worth it

Nothing to cut — the grass is barely growing (growth potential 0.09). Conditions themselves are fine.

Today morning is your first decent window.

Next mow

Today 8am–7pm

Verdict: Prime time, >95% chance it holds

temperature — 10°C

The next 10 days

Each row is a day, morning on the left. The more solid a block, the more of the forecast runs agree you can mow. Open a day for the hour-by-hour forecast behind it.

  1. Monday 19 October: 11 hours worth using. 8am–7pm — temperature — 10°C
    Monday 19 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———>95%>95%>95%>95%>95%>95%>95%>95%>95%>95%>95%——
    VerdictdarkdarkdarkPrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timedarkdark
    Rainchance0%0%0%2%0%0%0%0%0%0%0%0%0%0%0%0%
    Rainmm————————————————
    Grassdrydrydrydrydrydrydrydrydrydrydrydrydrydrydrydry
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm
    Temp8°8°8°8°9°10°12°13°14°14°14°14°14°12°11°10°
    Windkm/h2333555335555676
    Daylight———✓✓✓✓✓✓✓✓✓✓✓——

    Growth: barely growing (growth potential 0.14). Enough to be worth cutting. Growth decides whether a cut is wanted, not how well it will go, so it is not one of the rows above and does not move the chances.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Monday 19 October · 8am–7pmConfident

    8am–7pm — temperature — 10°C

    >95% prime time — the chance it holds right through, not the chance at any one hour. Every forecast run agrees.

    Limiting factor:temperature

  2. Tuesday 20 October: 11 hours worth using. 8am–7pm — temperature — 11°C
    Tuesday 20 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———>95%>95%>95%>95%>95%>95%>95%>95%>95%>95%>95%——
    VerdictdarkdarkdarkPrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timedarkdark
    Rainchance0%0%0%0%0%0%0%0%0%0%0%0%0%0%0%0%
    Rainmm————————————————
    Grassdrydrydrydrydrydrydrydrydrydrydrydrydrydrydrydry
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm
    Temp7°7°7°7°9°11°13°14°16°17°16°16°14°12°11°10°
    Windkm/h91099101191010101112111097
    Daylight———✓✓✓✓✓✓✓✓✓✓✓——

    Growth: barely growing (growth potential 0.16). Enough to be worth cutting. Growth decides whether a cut is wanted, not how well it will go, so it is not one of the rows above and does not move the chances.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Tuesday 20 October · 8am–7pmConfident

    8am–7pm — temperature — 11°C

    >95% prime time — the chance it holds right through, not the chance at any one hour. Every forecast run agrees.

    Limiting factor:temperature

  3. Wednesday 21 October: 11 hours worth using. 8am–7pm — temperature — 12°C
    Wednesday 21 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———>95%>95%>95%>95%>95%>95%>95%>95%>95%>95%>95%——
    VerdictdarkdarkdarkPrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timedarkdark
    Rainchance0%0%0%0%0%0%0%0%0%0%0%0%0%0%0%0%
    Rainmm————————————————
    Grassdrydrydrydrydrydrydrydrydrydrydrydrydrydrydrydry
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm
    Temp8°8°8°8°10°12°14°16°18°18°19°18°17°14°13°12°
    Windkm/h5554214676655677
    Daylight———✓✓✓✓✓✓✓✓✓✓✓——

    Growth: growing slowly (growth potential 0.20). Enough to be worth cutting. Growth decides whether a cut is wanted, not how well it will go, so it is not one of the rows above and does not move the chances.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Wednesday 21 October · 8am–7pmConfident

    8am–7pm — temperature — 12°C

    >95% prime time — the chance it holds right through, not the chance at any one hour. Every forecast run agrees.

    Limiting factor:temperature

  4. Thursday 22 October: 11 hours worth using. 8am–7pm — temperature — 11°C
    Thursday 22 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———>95%>95%>95%>95%>95%>95%>95%95%90%90%85%——
    VerdictdarkdarkdarkPrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timePrime timeGood to godarkdark
    Rainchance0%0%0%0%0%0%0%0%3%1%6%7%7%11%9%20%
    Rainmm——————————0.1——0.10.10.2
    Grassdrydrydrydrydrydrydrydrydrydrydrydrydrydrydrydamp
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm
    Temp8°8°8°8°9°11°13°14°15°16°16°16°16°13°11°11°
    Windkm/h332112334435361310
    Daylight———✓✓✓✓✓✓✓✓✓✓✓——

    Growth: growing slowly (growth potential 0.20). Enough to be worth cutting. Growth decides whether a cut is wanted, not how well it will go, so it is not one of the rows above and does not move the chances.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Thursday 22 October · 8am–7pmConfident

    8am–7pm — temperature — 11°C

    75% good to go — the chance it holds right through, not the chance at any one hour. About 1 run in 4 hit rain.

    Limiting factor:temperature

  5. Friday 23 October: 6 hours worth using. 1pm–7pm — rain earlier that day, ground firm
    Friday 23 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———40%40%45%45%50%80%90%95%>95%>95%>95%——
    VerdictdarkdarkdarkTouch and goTouch and goTouch and goTouch and goTouch and goGood to goPrime timePrime timePrime timePrime timePrime timedarkdark
    Rainchance4%2%10%11%2%4%3%7%3%3%2%2%2%1%1%2%
    Rainmm——0.10.1————————————
    Grasswetwetwetwetwetwetwetdampdampdrydrydrydrydrydrydry
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm
    Temp10°10°10°9°10°10°12°13°14°15°15°14°13°12°11°9°
    Windkm/h7865554456810111076
    Daylight———✓✓✓✓✓✓✓✓✓✓✓——

    Growth: growing slowly (growth potential 0.20). Enough to be worth cutting. Growth decides whether a cut is wanted, not how well it will go, so it is not one of the rows above and does not move the chances.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Friday 23 October · 1pm–7pmLow confidence this far out

    1pm–7pm — rain earlier that day, ground firm

    75% good to go — the chance it holds right through, not the chance at any one hour. About 1 run in 4 found the grass too wet.

    Limiting factor:none

  6. Saturday 24 October: nothing to cut. Nothing to cut — the grass is barely growing (growth potential 0.09). Conditions themselves are fine.
    Saturday 24 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———70%70%75%80%75%70%70%70%75%70%65%——
    Verdictnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growing
    Rainchance4%4%4%5%6%8%6%12%13%7%13%8%11%11%17%12%
    Rainmm——0.10.10.10.10.10.20.10.10.20.10.10.20.30.2
    Grassdampdampdampdampdampdampdampdampdampdampdampdampdampdampdampdamp
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm
    Temp6°5°5°5°7°9°11°12°13°13°14°14°13°13°12°11°
    Windkm/h3322233332135667
    Daylight———✓✓✓✓✓✓✓✓✓✓✓——

    Growth: barely growing (growth potential 0.09). Not enough to be worth cutting, which is why no hour is recommended today whatever the weather does.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Saturday 24 OctoberLow confidence this far out

    Nothing to cut — the grass is barely growing (growth potential 0.09). Conditions themselves are fine.

    80% nothing to cut. About 1 run in 4 found the grass barely growing.

    Nothing to cut. The odds below describe the weather only — growth decides whether a cut is wanted, and it is judged separately.

    Limiting factor:growth

  7. Sunday 25 October: no hours worth using. No — 0.3mm of rain falling.
    Sunday 25 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———55%55%55%55%55%50%45%45%45%45%45%——
    VerdictdarkdarkdarkTouch and goTouch and goTouch and goTouch and goTouch and goTouch and goTouch and goTouch and goTouch and goTouch and goTouch and godarkdark
    Rainchance8%7%13%19%13%16%10%14%14%12%14%10%17%9%10%14%
    Rainmm0.20.10.20.30.20.20.10.10.10.20.20.10.30.10.10.2
    Grassdampdampdampdampdampdampdampdampwetwetwetwetwetwetwetwet
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm
    Temp9°9°8°8°8°8°9°9°10°10°10°11°11°10°9°8°
    Windkm/h121197665432123567
    Daylight———✓✓✓✓✓✓✓✓✓✓✓——

    Growth: barely growing (growth potential 0.13). Enough to be worth cutting. Growth decides whether a cut is wanted, not how well it will go, so it is not one of the rows above and does not move the chances.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Sunday 25 OctoberLow confidence this far out

    No — 0.3mm of rain falling.

    55% touch and go. About half the runs found the grass too wet.

    Limiting factor:grass wetness

  8. Monday 26 October: nothing to cut. Nothing to cut — the grass is barely growing (growth potential 0.07). Conditions themselves are fine.
    Monday 26 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———40%40%40%40%45%75%80%80%80%85%80%——
    Verdictnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growing
    Rainchance9%13%2%6%8%10%4%14%8%7%9%10%7%10%7%6%
    Rainmm0.10.2—0.10.10.1—0.10.10.10.10.10.10.20.2—
    Grasswetwetwetwetwetwetwetwetdampdampdampdampdrydampdampdamp
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm
    Temp6°6°6°6°7°9°10°12°13°13°13°12°11°10°9°8°
    Windkm/h766681012131313131313121110
    Daylight———✓✓✓✓✓✓✓✓✓✓✓——

    Growth: barely growing (growth potential 0.07). Not enough to be worth cutting, which is why no hour is recommended today whatever the weather does.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Monday 26 OctoberLow confidence this far out

    Nothing to cut — the grass is barely growing (growth potential 0.07). Conditions themselves are fine.

    85% nothing to cut. About 1 run in 6 found the grass barely growing.

    Nothing to cut. The odds below describe the weather only — growth decides whether a cut is wanted, and it is judged separately.

    Limiting factor:growth

  9. Tuesday 27 October: nothing to cut. Nothing to cut — the grass is barely growing (growth potential 0.09). Conditions themselves are fine.
    Tuesday 27 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———65%65%70%70%80%80%80%80%85%85%———
    Verdictnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growing
    Rainchance3%5%8%9%10%7%3%8%9%11%9%10%7%7%6%15%
    Rainmm0.1——0.10.10.1—0.10.10.20.10.20.10.10.10.2
    Grassdampdampdampdampdampdampdampdampdrydrydrydrydrydrydampdamp
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm
    Temp6°6°5°6°7°9°12°14°16°17°17°16°14°13°11°9°
    Windkm/h6656678889910101098
    Daylight———✓✓✓✓✓✓✓✓✓✓———

    Growth: barely growing (growth potential 0.09). Not enough to be worth cutting, which is why no hour is recommended today whatever the weather does.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Tuesday 27 OctoberLow confidence this far out

    Nothing to cut — the grass is barely growing (growth potential 0.09). Conditions themselves are fine.

    85% nothing to cut. About 1 run in 6 found the grass barely growing.

    Nothing to cut. The odds below describe the weather only — growth decides whether a cut is wanted, and it is judged separately.

    Limiting factor:growth

  10. Wednesday 28 October: nothing to cut. Nothing to cut — the grass is barely growing (growth potential 0.10). Conditions themselves are fine.
    Wednesday 28 October, hour by hour
    5am6am7am8am9am10am11ammidday1pm2pm3pm4pm5pm6pm7pm8pm
    Chance———65%65%65%65%65%70%75%75%70%————
    Verdictnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingnothing to cut — the grass is barely growingAlready goneAlready goneAlready goneAlready gone
    Rainchance2%6%8%7%6%8%8%11%6%12%13%16%····
    Rainmm—0.10.20.10.10.10.10.10.10.10.10.1····
    Grassdampdampdampdampdampdampdampdampdampdampdampdamp····
    Groundfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirmfirm····
    Temp6°6°5°6°7°9°11°13°14°15°15°15°····
    Windkm/h322122345555····
    Daylight———✓✓✓✓✓✓✓✓✓····

    Growth: barely growing (growth potential 0.10). Not enough to be worth cutting, which is why no hour is recommended today whatever the weather does.Chance is the share of 82 forecast runs — the same weather models re-run from slightly different starting conditions — in which you could have mowed that hour. The rows below it are what those runs expect on average, which is why an hour can look reasonable line by line and still fall short: the chance only counts runs where everything came together at once. Hover any cell for what the runs that ruled it out actually hit.

    Wednesday 28 OctoberLow confidence this far out

    Nothing to cut — the grass is barely growing (growth potential 0.10). Conditions themselves are fine.

    75% nothing to cut. About 1 run in 4 found the grass barely growing.

    Nothing to cut. The odds below describe the weather only — growth decides whether a cut is wanted, and it is judged separately.

    Limiting factor:growth

good to go touch and go dark, frost or snow already goneFainter means fewer forecast runs agree.

How you feel about mowing

Sensible middle ground.

Petrol or battery. The baseline.

Growth

How fast it is growing, and when it will need cutting again.

14%Barely growing

Of the fastest this grass could grow. The turf-industry measure, from today's temperature and day length.

The lawn is barely growing, so it does not need cutting. Leave it — taking leaf off a sward that cannot replace it costs more than it gives.

Held back by both temperature and short days — 10.7 hours of daylight at 10°C.

Over the next 10 days
about 5mm of leaf
Next cut due
not within the next ten days

This only knows temperature and day length. Feeding, watering, shade and cutting height all move it, so treat it as a rough guide.

Worked out from the PACE Turf growth potential model and day length —how and why.

Seeding

Soil temperature at germination depth, and when the window opens.

Soil temperature in Seattle, Washington

50°F10.2°C

at 6cm — germination depth

Too cold to seed — 10.2°C at 6cm and not warming.

Cooling over the next 10 days.

Cross-checks against an independent estimate from air temperature (11.2°C), which agrees to within 0.2°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 use 12.5°C as the seeding threshold.

Thresholds for every species

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 neededDays to sprout
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

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 not growing fast enough to make much use of 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.

Why timing beats product choice

Seattle, Washington in detail

Soil temperature in Seattle, Washington is currently 10.2°C at 6cm, and falling about 7.1°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. Too cold to seed — 10.2°C at 6cm and not warming.

5 of the next 10 days look workable. As for the weekend: nothing doing. Nothing to cut — the grass is barely growing (growth potential 0.09). Conditions themselves are fine.

The next recommended window in Seattle opens at 8am on Monday 19 October, because that is first light. Underfoot, the ground reads as firm after 4mm rain over the last week, medium (loam) soil.

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Chances counted across 82 forecast runs from NCEP GEFS, 25km and ECMWF IFS ensemble, 25km. Forecast from Open-Meteo, refreshed through the day. Soil temperature is modelled, not measured — how that works and where the thresholds come from.