暖かくなった

became warm

→ 暖かい
phrase Rare #32,903
became warm Used when the weather, air, or a place has become warm or warmer. 暖かく is the adverbial form of 暖かい, and なった means “became.”
JA: 春になって、だんだん暖かくなった。
EN: Now that spring has arrived, it has gradually become warmer.

天候が暖かくなった

The weather has warmed up.

もう暖かくなったので外出できる

It’s warm enough now to go out.

教室やっと暖かくなった

The classroom has finally warmed up.

空気が暖かくなった

The air has warmed up.

一瞬とても暖かくなったと思う今度は冷たくてひどいことになる

Just when it seems to get warm for a moment, it turns cold again and becomes awful.

— エブリシング・エブリウェア・オール・アット・ワンス (2022)