This speech from the Porter in macbeth is about the impact of alcohol on the (male, in this case) libido but I think it applies pretty well to hot weather too.
Lechery, sir, it provokes, and unprovokes;
it provokes the desire, but it takes
away the performance: therefore, (it)
may be said to be an equivocator with lechery:
it makes him, and it mars him; it sets
him on, and it takes him off; it persuades him,
and disheartens him; makes him stand to, and
not stand to