noun
Describes oppressive, often unbearable heat. More literary than 猛暑 (もうしょ) and less common in everyday conversation.
夏の苦熱に耐えかねて、エアコンをつけた。
Unable to bear the intense summer heat, I turned on the air conditioner.
この地方の苦熱は想像を絶する。
The scorching heat of this region is beyond imagination.
Compound of 苦 (く, 'suffering') and 熱 (ねつ, 'heat'). The exact historical derivation is uncertain, but the word literally suggests 'suffering from heat'.