Field Guide / Clouds & Weather Signs
Cirrocumulus
mackerel sky
A high sky of tiny white ripples, like fish scales. It is fairly rare and short-lived, and it often signals changing weather.
- Height
- High Clouds
- Abbreviation
- Cc
- Typical altitude
- Above about 20,000 ft (6,000 m); made of ice crystals
- Usually means
- Weather changing
How to recognize it
- Very small white cloudlets, each smaller than a fingertip held at arm's length, in rows or ripples.
- White with no gray shading, since they are so thin.
- Often appears in patches with blue sky between.
What it usually means
- Often a short-lived, transitional cloud that appears with cirrus ahead of a change.
- An old saying warns that a mackerel sky does not stay dry or wet for long. Treat it as a hint that the weather may soon change.
- In cold weather it can mean cold but fair conditions.
What to do outdoors
- Keep an eye on the sky and the forecast, since conditions can change in a day.
- Carry layers if you are going out for a long time.
Often confused with
- Altocumulus: larger cloudlets with gray shading on the undersides.
Field notes
Cirrocumulus is beautiful but brief, and it can be hard to tell from small altocumulus. The size of the cloudlets and the lack of shading are the clues.
Because it usually appears with other high clouds, it makes sense to read it together with them.
Related guides
Cloud signs are rough guides, not forecasts. Always check the National Weather Service forecast at weather.gov before and during a trip, carry a way to receive alerts, and treat any watch or warning as a reason to change your plans. If you can hear thunder, you are close enough to be struck by lightning.