Above the clouds, on purpose

Inversa forecasts cloud inversions: the mornings when the valleys fill with cloud and the summits sit above it in sunshine. It scores the dawn at summits and viewpoints around the world for the next three days, and shows where the sun will rise and how the sky should look.

How the score works

For every hour, Inversa reads the weather model's picture of the atmosphere above each hill and looks for five things together:

Cloud or fog below the summit, trapped in the valleys
The summit clear of it, with the cloud top a safe margin below
Dry, clear air above, so you're in sunshine rather than more cloud
A temperature inversion, where air gets warmer with height and puts a lid on the cloud
Light winds and high pressure, which let the layer settle instead of mixing away

All five need to line up, so the score drops quickly when one is missing.

60+ Likely35–59 Possible15–34 Outside chanceUnder 15 Unlikely

Very shallow valley fog is hard for weather models to see, so treat small hills and deep, narrow valleys as a guide. You can set the summit and valley heights for any place you add.

Sunrise and sunset colour

Separately from the inversion score, every place gets a colour score from 0 to 100 for sunrise and sunset, whether or not there's an inversion. It looks at high cloud to catch the colour, mid-level cloud that blocks it, cloud at summit height that could hide the sun, and how hazy the air is. A clear sky scores in the middle: clean golden light, but little colour overhead. Each day also shows first light on the summit, blue hour, golden hour, and the moon's phase and position at dawn.

Maps

Switch the hill list to Map to see every place coloured by its score, for inversions or for sunrise and sunset colour, and tap a dot to open its forecast. Each forecast also has a planning map: a topographic map of the viewpoint with lines showing where the sun rises and sets, which way your shadow falls at sunrise (where to look for a Brocken spectre), and where the moon is at dawn.

Put it on your home screen

iPhone and iPad

Open getinversa.com in Safari, tap the Share button, then Add to Home Screen.

Android

Open it in Chrome, tap the ⋮ menu, then Install app or Add to Home screen.

Computer

In Chrome or Edge, click the install icon at the right of the address bar, or the Install app button on the forecast page.

It opens full screen like any other app and always shows the latest version. With no signal, it shows your last forecast.

Where the data comes from

Forecasts come from Open-Meteo, which picks the best national weather model for each place: the Met Office in the UK, Météo-France, Germany's DWD, NOAA in the US, JMA in Japan and others. Sunrise times and directions are calculated for each summit. Weather data is licensed under CC BY 4.0.

Stay safe

Inversa is a guide for planning, not a mountain safety forecast. Inversion mornings are often cold and icy on top, and cloud can rise quickly. Check a mountain forecast such as MWIS or the Met Office, and go prepared.