Clouds are made up of millions of tiny water droplets. Clouds are made when quite warm, moist air rises into the sky where it cools down and condenses. Clouds can form in a few minutes or over a number of hours. There are many different types of cloud and looking at them can help you to predict the weather.
The amount of cloud in the sky is measured in eighths (or oktas by meteorologists). Simple observation can be made such as
Clear – no cloud cover
Partly cloudy – less than half cloud cover
Mainly cloudy – more than half cloud cover but with some breaks in the cloud
Overcast – complete cloud cover
Cloud can be measured through a number of observations. Consider whether the cloud is:
| HIGH | (5,500-14,000 meters) Includes: Cirrus, cirrocumulus, and cirrostratus |
|---|---|
| MEDIUM | (2,000-7,000 meters) Includes: Altocumulus, altostratus, and nimbostratus |
| LOW | (below 2,000 meters) Includes: Stratocumulus, Stratus, Cumulus, and Cumulonimbus |
| Altitude | Name | Colour | Description | Weather |
|---|---|---|---|---|
| HIGH | Cirrostratus | White Whitish | Thin silky and feathery Fat, smooth transparent sheet | Fair Worsening |
| MEDIUM | Altocumulus Altostratus Nimbostratus | White/grey Greyish Dark grey | Layers and waves often separated by blue sky Thin sheets/layers Thick sheets | Fair Rain on way Continuous rain/snow |
| LOW | Stratocumulus Stratus Cumulus Cumulonimbus | Grey/white Grey Grey/white Grey/white | Layers in rounded rolls. No breaks. Thin sheet blanketing sky Puffy clouds Very tall puffy clouds | Dry/dull Drizzle Good Storms. Heavy rain/hail/snow |
