暑い【あつい】
hot, warm, sultry, heated, passionate, impassioned, burning (desire, etc.), on everybody's mind, on the radar, du jour, interested (gaze, etc.)
暑さ【あつさ】
heat (of the weather), hotness
残暑【ざんしょ】
late summer heat, lingering summer heat
避暑【ひしょ】
escaping the summer heat, going somewhere cooler during the summer, summering
蒸し暑い【むしあつい】
humid, sultry
酷暑【こくしょ】
intense heat, severe heat
猛暑【もうしょ】
heat wave, fierce heat
暑中【しょちゅう】
height of summer, high summer, hottest part of the summer
炎暑【えんしょ】
heat wave, intense heat