Mow Day

The lawn is getting long, you have an hour free this afternoon, and the sky looks like it might not last. Mow Day answers the only question that matters: is there room to mow, and when?

A verdict, not a weather chart

No radar to squint at, no humidity graphs to interpret. One clear answer in plain words — great time to mow, good time to mow, grass likely damp, rain close behind, or better to wait — with the reason in one sentence underneath.

It fits the mow you actually do

Tell it how long your mow takes and which hours you are free, and it stops offering you gaps you cannot use. A window is only a window if the whole job fits inside it.

Worked out from the grass up, and shown

Mow Day combines the published FAO-56 Penman–Monteith reference evapotranspiration calculation — the UN Food and Agriculture Organization's method for a clipped grass surface — with its own assumptions about water on the grass and in the topsoil. Each forecast hour's temperature, dew point, wind and solar radiation go into it, to estimate how quickly wet blades may dry.

The ground gets a sum of its own: a water balance for the top 10 cm of soil, after FAO-56's surface-layer method, with loam or clay chosen by one setting. That is how the app can tell grass that has dried off from ground that is likely still soft underfoot.

Tap "How this is worked out" under any verdict and the app shows its working: the forecast for that hour, the equation with its numbers, the water estimated on the blades and in the topsoil. Every figure is labeled as an estimate from a forecast, and the sheet explains the forecast inputs and the key assumptions that are the app's own, not FAO's.

What you get

• The next estimated mowing window, with an estimated start-by time: "9:30 am – 1 pm."
• A start-by time, and what closes the door: rain, the light going, or the end of the hours you set.
• Whether the grass has had a chance to dry — after rain, and after a heavy dew — with an estimate of when it should.
• The next three days as mowing advice, with the best day tagged.
• One quiet, optional alert: a heads-up the evening before a good mowing day, and a nudge when the window opens. Nothing else, ever.
• Two things about your lawn that change the answer: shade, and ground that stays soft after rain (clay rather than loam in the soil sum).
• The working behind every verdict, one tap away.
• A last-checked note when you are offline, so you know how fresh the advice is.

Honest about what a forecast can tell you

A forecast is a guess, and Mow Day says so. It cannot see your lawn: not how long the grass is, not how soft the ground is underfoot, and not exactly what fell on it before the forecast began — and when it cannot see far enough back, it tells you that too, rather than implying dry ground. Wet grass tears instead of cutting and clogs a mower; the app will say the grass is likely damp, and leave the last look to you.

Built for people who mow their own lawn

Made in Australia, and it works anywhere there is weather and grass.

Quietly respectful

No accounts, no tracking, no lawn diary. Your location is used to fetch the forecast and to name your town — we run no servers, and nothing you do in the app reaches us. Free with a single unobtrusive banner; one small one-time purchase removes it forever. No subscriptions, ever.

Weather data by WeatherAPI.com. Mow Day is an informational tool — it reads forecasts, it does not control the weather, and it is not a safety device.

Recent changes:
Ads are off for now. New in Settings: three ways to say thanks, each a one-time purchase — and any one of them also keeps the app ad-free for good.