Four · Over you

The weather.

Most forecasts give you an icon and a number and leave you to guess how much to trust it. We would rather answer the question you actually asked — can I see the sky tonight, when should I do this outside, what are the odds — and tell you how confident the answer is.

National modelsLive observationsOdds, not iconsConfidence stated
25%50%75%PROBABILITY OF CLEAR SKY · ENSEMBLE MEMBERS AND MEAN · 72 H
0h12h24h36h48h60h72 hCHANCE OF CLEAR SKY, BY HOUR

Three days, one hour at a time

The whole forecast horizon in a single figure — seventy-two hours, one spoke each, rather than seventy-two rows you have to read down.

  • Now at the top, then clockwise. The marks read 0h, 12h, 24h, 36h, 48h and 60h; the ring closes at seventy-two, which is as far as the national models are worth quoting.
  • Length is the probability. The inner edge is nought and the four faint rings are the quarter marks — 25, 50, 75 and 100 per cent chance of clear sky.
  • A run of long spokes is your window. You are not meant to read values off it. You are looking for the arc where the odds hold up, and that arc is the block of hours worth planning around.
What we measure

Ten things, with the disagreement kept in.

Forecasts are built from national numerical weather models and checked against live airport observations. Where the models disagree, we do not hide it — the spread between them is the confidence figure we hand back.

+0h+12h+24h+36h+48h+60hTHE ANSWER AND HOW FAR THE MODELS DISAGREE · WIDER IS LESS SURE

How far ahead is worth trusting

The same forecast as an answer and a doubt: the dark line is the figure, the pale band is how far the models still disagree at that hour.

  • One bar every two hours. Thirty-six of them, from now to three days out.
  • Deep band, weak answer. Where the models land on the same number it stays thin; where they scatter it opens, and we show that rather than averaging it away.
  • Six times deeper by day three. Not the drawing hedging — that is what a three-day forecast is worth, and you should see it before you plan around one.
A clear night sky full of stars, rendered
A clear night — rendered, not photographed
The question it answers

Will I see it tonight, and how sure are you?

That is one question, not two, and Weather answers it as one. The Perseid peak over your roof, the cloud that will be sitting on it at that hour, and a confidence figure taken from how far the national models actually disagree with each other — in a single sentence, for your point rather than your region.

  • Tonight — is the sky worth going outside for
  • The window — the best hours to do the thing
  • The odds — a probability, not an icon
  • The confidence — how much the models disagree
Ensemble members diverging over the forecast horizon; their spread is the confidence figure
Every thin line is one national model run. They agree about tonight and fan apart by the weekend — the width of that fan is the confidence figure.
In development

The forecast, as a to-do.

Chores turns the forecast into “do it now”: the window to hang the washing, mow, paint, wash the car, go out with a telescope. Beyond it, weather lives inside the other apps — the night worth going out for, the daylight your clock will actually get.

The apps →
  • ChoresThe forecast turned into “do it now”.
How it is carried

Weather is carried, not printed.

A forecast is out of date before the ink dries, so Weather arrives in the forms that stay current: a number in the app, a window in the planner’s day, an alarm that fires when the cloud actually clears, a line in your calendar the evening before. The climate normals behind it — the average sky for this place in this month — do print, and they sit in the almanacs.

Build with it

The odds, in your own code.

Forthcoming

Point forecasts and quantities, the odds of a condition rather than a yes/no, working windows, pressure trend, live observations — and a confidence figure that comes from how far the models actually disagree. Ask for tonight’s sky, a working window, an hourly forecast, or the confidence behind any of it, for any place.

Want it wired into the system that actually makes the call — a dispatcher, a booking page, a site diary — or built into software of your own? Ask for that instead. And if you have looked at this and concluded it could not be done, bring it here and let us give it a second thought.

Tell us what you are building    API, integrations and bespoke software →

The rest of the arc
Above youSkyWhat is up there, behind the cloud.Inside youBodyHow much of that light you actually get.Beneath youEarthThe ground this weather sits over.