The total amount of cloud as a percentage is derived from looking at cloud cover throughout the atmosphere and estimating how these combine when looked at from the ground.
The amount of cloud cover is given as a percentage and is calculated for different levels in a way that is closely related to moisture content, temperature and pressure.
You can find out a little more about the cloud cover at different levels by holding your cursor over the amount for that time frame and a popup will show you the amount of cloud in % at low, middle and high points in the atmosphere as well as identifying the level we feel is most significant to people on the ground.
Understanding these and looking closely at them can help you to plan better your activities – if most of the cloud is high level and probably thin, it may impact what activities you will undertake outside. However if the cloud is 100% cover at mid and low levels you could surmise that it will be very dull and hill and mountains will be shrouded in cloud.
We considered that it may be helpful to give you this additional information so that you can better plan your activities.
There is a lot more to this than just the total cloud amount and when the weather is important, we would suggest that you view all the information you can to help you with your decision making.