Clear, cloudless weather; a bright, sunny sky with no clouds.
今日は快晴なのでピクニックに行こう。
It's clear weather today, so let's go on a picnic.
快晴の空に富士山がよく見える。
Mount Fuji is clearly visible under the cloudless sky.
行楽日和の快晴で、海岸は人で賑わっていた。
It was a perfect sunny day for outings, and the coast was crowded.