Apreciado Cristóbal: Greetings, my friend! If you go to "Bob's Lessons"--as I call them!--you'll see that higher outside temps do not call for a thicker (i.e. more viscosity) oil. The main consideration is how well it flows through the minute engine passages in order to dissipate heat more efficiently, and not just to lubricate the moving parts, which lower- viscosity oils do just as well as higher-viscosity ones.
(Bob: if you read this, correct me if I'm wrong, please!)