I doubt the hot weather can do that. maybe the beginning of the Anthracnose disease (although i dont see black dots). i dont really know. someone in here more knowledgable will answer you.
EDIT: actually it might just be sunscald: http://www.google.com/search?um=1&hl=en&biw=1291&bih=538&tbm=isch&sa=1&q=sunscald+on+peppers&oq=sunscald+&aq=2&aqi=g10&aql=&gs_sm=e&gs_upl=7582l9267l0l9l9l0l1l1l0l203l1217l1.5.2
I did google it before posting, but I did not see any black spots on the pictures of sunscald I saw, that is what worried me. There is a single black spot on the wound.