A red sky at night often means clear weather tomorrow; a red sky in the morning often signals rain — an old weather proverb.
今夜はきれいな夕焼けだ。天気予報もいいし、夕焼けは晴れ朝焼けは雨の通りだね。
There's a beautiful sunset tonight. The forecast is good too — as the proverb says, red sky at night, shepherd's delight.
朝焼けが出ている。今日は傘を持って行ったほうがいい。夕焼けは晴れ朝焼けは雨だ。
There's a red sunrise. You should take an umbrella today. Red sky in the morning often means rain.