This is the 8725th most frequent Japanese word.
暖かく
Warmly; warmly (weather or to touch).
暖かい describes the comforting warmth of spring sunlight.
春の日差しはとても暖かい。
The spring sunlight is very warm.
暖かく is used metaphorically to describe emotional warmth.
彼女の笑顔は心を暖かくする。
Her smile warms the heart.
暖かく refers to adjusting the temperature to be comfortably warm.