訓 あたた(かい),あたた(まる) ・ 音 ダン
漢越音: noãn
The sun 日 gives the meaning: this is the warmth of sunshine and air, while 温 with its water radical is warmth you touch in liquid. See danbou, indoor heating.
Stroke data: KanjiVG (CC BY-SA 3.0) — kanjivg.tagaini.net
今日は暖かい日です。 (きょうはあたたかいひです)
Today is a warm day.