What is a Madrid mister?

Answer 1

This most likely refers to a patron cooling system used in cafes and bars in Madrid and now further South in Spain and even in Las Vegas.

It consists of a very thin cable with small tight nozzles at roughly 25cm (12in) intervals, attached to a water supply. Every 15 to 20 seconds, an extremely fine mist puffs out of these nozzles - much like the water from a cool humidifier. The water fills the air and has an impressive ability to cool you down. It's actually more effective in some ways than an air condition from the point of view that you feel cooler immediately. It is used almost exclusively in open spaces, with the effect that in a space which cannot be effectively temperature, patrons (or other users) can feel comfortable.

I haven't heard this name, but this is what I call it, so it is very possibly a common name.