The moon in clear weather in Portugal
In clear or clear weather, we understand the cloudless sky in meteorology.
The weather forecast uses the term for a virtually cloudless air at night. Clear can be related to sight; especially in polar air from the northern latitudes, the view is mostly good because there is little pollution in that air. However, when the stars are striking in the sky, it can mean a fast end to the beautiful weather. This indicates the supply of cold, very dry air in the upper layers of the atmosphere.
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