- 温泉【おんせん】 - hot spring, onsen, hot spring resort, hot spring spa 
- 温度【おんど】 - temperature 
- 温める【あたためる】 - to warm (up), to heat (up), to sit on (an idea, plan, etc.), to keep to oneself, to nurse, to mull over, to renew (an old friendship), to take for oneself 
- 温める【ぬくめる】 - to warm (up), to heat (up) 
- 気温【きおん】 - air temperature 
- 体温【たいおん】 - temperature, body temperature (human, animal) 
- 温暖【おんだん】 - warm, mild, temperate 
- 高温【こうおん】 - high temperature 
- 温室【おんしつ】 - greenhouse, hothouse, conservatory, glasshouse 
- 低温【ていおん】 - low temperature 
- 温まる【あたたまる】 - to warm oneself, to sun oneself, to warm up, to get warm 
- 保温【ほおん】 - retaining warmth, keeping heat in, heat insulation 
- 温帯【おんたい】 - temperate zone 
- 温和【おんわ】 - mild (climate), temperate, clement, pleasant, agreeable, gentle (nature, personality, etc.), mild, quiet, pleasant, moderate (statement, measure, etc.), mild, temperate 
- 体温計【たいおんけい】 - (clinical) thermometer 
- 温床【おんしょう】 - hotbed, breeding ground 
- 水温【すいおん】 - water temperature 
- 温存【おんぞん】 - preservation, retainment, keeping 
- 温厚【おんこう】 - gentle, mild-mannered 
- 室温【しつおん】 - room temperature