温暖 (wēn nuǎn) is a versatile word for 'warm' used for both physical temperature and emotional warmth (e.g., a warm room or a warm heart). It is more formal and literary than the everyday 暖和 (nuǎn huo), which is the go-to word for pleasant weather or clothing. 温馨 (wēn xīn) specifically describes a cozy, heartwarming atmosphere, not physical temperature.