I've lived in Seville for 39 years (my husband's from Seville), after spending the first 25 years of my life in the northeast of the US. ittedly it was a big change of climate for me, but even after all these years in Seville I can say that I REALLY DISLIKE the summer heat here. Life totally changes in July and August because you really cannot be out and about without totally melting from about 1 pm to 8 pm. So you have to adapt your lifestyle. You run all of your errands as early in the mornings as possible. You always walk on the shady side of the street. Your kids go out to play at night. Social life (for kids and adults) starts happening no earlier than about 9pm. During the hottest time of the day you stay home with windows closed, the blinds down against the sun and with the A/C running. If you have kids they go bonkers because they can't go out to play all day long. The only way to go out is if you have access to a pool. For all these reasons many many people do whatever they can to get away to the beach for as much of the summer as possible. Which means that the city empties out and there's not much going on.
One positive thing is that usually nights cool off to very pleasant temperatures. That's why there are so many eating establishments with outdoor seating, which allows people to sit outside at night having tapas and a beer until quite late while the kids play nearby. And at night you can open the windows and turn off the A/C. We sleep with windows open and a ceiling fan running probably 90% of the time. The other 10% of the time we do run the A/C all night - but there are plenty of people who don't have A/C in the bedrooms.
By the way, people who come to Seville in the summer have often been told that "everything is closed", but that's really not the case. Maybe there are fewer people working, but there are also fewer customers. It's rare for a place to totally close down for a month.
Aside from those 2 months or so of burning heat, Seville usually has lovely weather. It does get cold for a month or two in the winter (and houses usually aren't winterized) but personally I enjoy the change. No place is perfect, and for me the positives of Seville far outweigh the negatives.
