Specifically the hottest part of summer. Often used in fixed expressions like 暑中 (しょちゅう).
At the height of summer, I go to the mountains seeking a cool place.
lingering summer heat; late-summer heat
height of summer; hottest part of summer
intense heat; severe heat; extreme heat
escaping the summer heat; summering in a cooler place
summer heat; heat of summer
summer heat; hot weather · heatstroke
Limit of Heat; solar term around August 23
severe heat; intense heat; oppressive heat
extreme heat; intense heat
approach of the hot season; approaching the hottest time of the year
"major heat" solar term (approx. July 23) · blistering heat; intense summer heat
cold and heat; winter and summer
Minor Heat; 11th solar term
hot summer
intense heat; peak of summer's heat
The kanji 暑 is a phono-semantic compound: 日 (sun) + 者 (phonetic, also suggesting 'to gather'). It originally meant 'hot weather'. The reading しょ is the on'yomi.