Kelvin — Living Forecast

Kelvin turns the entire day into a single field of color, shaped by temperature. Drag across it to move through time.

Most weather apps hand you a wall of cards. Kelvin draws the day instead.

The forecast is one continuous color mass across the foot of the screen. Its crest is the temperature and its color is the temperature — cold indigo through to hot magenta — so the shape of the day is legible before you read a single number. Drag your finger across it and you move through time; the huge thin numeral counts with you.

Nothing else on the screen competes with it. No cards, no rows, no weather icons, no tabs.

WHEN TO GO OUT Tell Kelvin the weather you like — a temperature, how much either side of it, and whether you want it rain-free, calm, dry or in daylight. It reads the next seven days hour by hour and tells you the next stretch that matches. The whole week is drawn as a grid of hours so you can see why, not just be told.

THE MAP Seven layers, and not one of them asks you for an API key. Rain radar you can drag back and forward through the last two hours. NEXRAD base reflectivity over the United States. Infrared cloud tops from orbit. Forecast rainfall in six-hour steps out to three days. Active watches and warnings. Tropical cyclone tracks and their forecast cones. Wildfire perimeters and how much of each line is held. All of it on a map that shares the app's own palette, so a color means the same thing everywhere.

READINGS, NOT DASHBOARDS Feels-like, wind and gusts, UV, moon phase, dew point, pressure and its trend, visibility and humidity — present, quiet, and out of the way of the thing you came to read.

EVERYWHERE ELSE Home Screen and Lock Screen widgets, a Live Activity while rain is on the way, and Apple Watch complications. All drawn from the same band.

BUILT PROPERLY Dark mode that turns the paper over rather than inverting it. Full Dynamic Type, including the accessibility sizes. Every color in the app is measured against the WCAG contrast floor, and there are tests that fail if one drifts under it.

THEMES Kelvin comes with its own palette, free forever. Four more are available as separate one-time purchases, and each is a real deviation rather than a hue shift: Infrared reads the day as a thermal camera. Opal is iridescent pastel on cool gray. Ultraviolet is not printed but lit, like a blacklight in a dark room. Graphite is a black mineral where color appears only where the light bends. You can see any of them full-screen, on your own forecast, before buying.

PRICE Kelvin is free for seven days, in full. After that, one payment of $9.99 keeps all of it — the forecast, the map, the comfort week, the widgets and the watch — and covers everything Kelvin adds later. It is not a subscription. Themes are sold separately at $4.99 each and are not included in the trial or in the one-time purchase.

Weather data from Apple Weather. Radar from RainViewer, warnings from the National Weather Service, satellite imagery from NASA.