Miami is hotter and more humid than Spain in summer but they don’t take siestas. Siestas aren’t as popular as they used to be. It worked ok. in the old Spain when people didn’t travel far to work. Now many more are commuting, also most of the large chain stores open throughout the day.
Yes the commute killed off the siesta in Madrid – what’s the point in having a 3 hour break at lunchtime when you’ve got nowhere to go? Problem is that people are still expected to work later (probably why they take the long coffee breaks)