It's Not the Heat, it's the Character
For the record, if you live in the Pacific Northwest, and you are reading this somewhere without air conditioning, you are probably sweating. Strange thing with weather, however, is that stories of heat waves or cold streaks are about as inspiring as stories of someone coming down with and then getting over a cough. One thing everyone knows for certain about weather—it will change. That is hot or cold or wet or dry on a given day is almost never of any consequence to anyone other than the one who is hot or cold or wet or dry. Unless, that is, the hot or cold or wet or dry precipitated some kind of change within the person experiencing it. Now we have a story. If someone were climbing a mountain, say, the extreme cold of the mountain becomes one more thing the climber must endure, and perhaps he begins bitter but by the end of his climb comes to accept the cold the way a character in a different story might come to accept death.
Weather is also useful when it serves as a (hopefully) subtle reminder of something the character is feeling. In A Farewell to Arms it is always raining when something bad happens. In Finding Nouf, a mystery set in modern day Saudi Arabia, Zoë Ferraris fills the novel with the relentless heat of the desert, which serves as a nice backdrop for the suffocating social requirements central to the novel.
All of which reminds me yet again that setting description simply for description sake is never as compelling as descriptions that in some way reveal what a character is feeling. Feeling is all. Weather is yet another physical fact surrounding your characters, the same as the peeling paint, the barking dog, and the green grass. What you choose to describe has everything to do with what the characters exposed to it are feeling at the moment.