Cloud cover: UV radiation levels are highest under cloudless skies but even with cloud cover, they can be high.

云量：在晴朗无云的天空，紫外线辐射水平最高。但是，即使有云层，紫外线辐射水平也可以很高。

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Under cloudless skies, the surface gives up its moisture, making the ground level hotter and drier while not increasing the chances of rain.

在万里无云的天空下，地表水分蒸发，使地表更热、更干燥而无法增加形成雨的机会。

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Under cloudless skies the surface heats and gives up its moisture, making things at ground level hotter and drier while not increasing the chances of rain.

这块万里无云的天空下，地表温度上升、失去水分，从而造成地面上的物质越变越热、愈加干燥，但降雨的机会却丝毫未增加。

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It was a perfect evening for football: cloudless skies and a light fall breeze.

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Surrey have had an appalling season, and their batting under cloudless skies on Friday was shocking, even taking into account the absence through injury of Jon Batty.

BBC: Nottinghamshire go top with win

You will need cloudless, dark skies away from city lights to see the shower.

FORBES: How To See The Quadrantids Meteor Shower