There is a heat wave in Paris right now, although not, blessedly, in the mountains of the Rockies where I am lodged for another few days. It's not a coincidence that I am avoiding being there in the month of August!
Paris is ill equipped for the heat. Although the past ten years have been increasingly hot, you still find many tiny and even large shops with no air-conditioning. I always wonder why a shop-owner doesn't realize that people don't want to come in if it's too hot. Very few residential units are cooled either. It can be stifling hot in a Paris apartment, yet you will still find French people saying that air-conditioning (la clim) makes you sick. If that were true, the entire southern United States would be ill constantly.
In 2003 I returned from a miserably hot, muggy Houston, a town my mother likes to say did not really exist before air-conditioning, in early August, only to find Paris even hotter than southern Texas. The difference is that Houston is used to dealing with the heat, and every place is air-conditioned, often so fiercely that I take a sweater everywhere. In Paris the only weapons against the heat and humidity were open windows and refrigerators.
It was over 100º F in Paris for day after day-- ten days, I believe. My own apartment building is made of thick stone and the apartment has high ceilings, so that walking into the building was a relief, but even so the days were insufferably hot. I took several showers a day and planted myself in front of a fan to work with wet hair and wet clothes. During this period, 14,000 people died in France (including Hitler's British buddy Diana Mitford, whom I once met when she was already in her 90s-- she was still very beautiful). Across Europe, 70,000 people died. Most who died in France were old people, often left behind in small hot Paris apartments while their children and grandchildren holidayed in cooler places. Quite a few were found dead in front of their opened refrigerators, where they had tried to find a bit of cool air.
A wave of guilt after this caused the French authorities to try to identify vulnerable people for future canicules. Apparently this year a scam directed at old people is that "municipal employees" will appear at their door pretending to be asking questions related to their safety during a heat wave, but really casing the joint and stealing things.