The state of the atmosphere — overall weather conditions including temperature, humidity, wind, etc.
今日は天気がいいから散歩に行こう。
The weather is nice today, so let's go for a walk.
天気予報で明日の天気を確認してから出かけたほうがいい。
You should check the weather forecast for tomorrow before going out.
急に天気が変わって、洗濯物を取り込まなければならなかった。
The weather suddenly changed, so I had to bring in the laundry.
Fine or fair weather — used to indicate good, typically sunny weather.
遠足の日は天気に恵まれて、みんな楽しめた。
We were blessed with good weather on the excursion day, and everyone enjoyed it.
週末は天気が持ちそうだからピクニックに行こう。
The weather looks like it will hold this weekend, so let's go on a picnic.
今日は天気が最高で、海は穏やかだった。
The weather was perfect today and the sea was calm.