“Partly cloudy” means different things to different people. Weather observers needed something more exact, so they use oktas.
The sky is divided into eight equal parts. Each part covered by cloud is one okta.
- 0 oktas: clear sky
- 1 to 2 oktas: mostly clear, a few clouds
- 3 to 4 oktas: partly cloudy
- 5 to 7 oktas: mostly cloudy
- 8 oktas: overcast
Where you’ll see it
Airport weather reports for pilots (called METARs) describe cloud layers with codes based on this scale: FEW (1 to 2 oktas), SCT for scattered (3 to 4), BKN for broken (5 to 7) and OVC for overcast (8). A report that says BKN030 means a broken cloud layer at 3,000 feet above the ground.
Why weather apps disagree about clouds
Different apps round the numbers differently and some use satellite estimates instead of a person looking up. One app’s “partly cloudy” can be another’s “mostly cloudy” for the same sky.
Try it yourself
Next time you’re outside, stand where you can see the whole sky, imagine it cut into eight slices like a pie, and count how many are covered. With a little practice you’ll be within an okta of the official report. On the open prairie, with the whole sky in view, it’s easier than almost anywhere.
Compare your count with the conditions at West Lethbridge Weather and the airport report on our Forecasts, warnings & radar page.