Guinness Stout is a thick, rich beer and the climate of Ireland is cool and wet. Corona, on the other hand, is light and thin, and the climate of Mexico is hot and dry. This is not a coincidence. Drinking Guinness in Mexico would seem peculiar and masochistic, because that thick creamy stout would sit in your belly like a stack of bricks in the sun and the heat. Even in a northern climate like Minnesota, Guinness is something you would drink in the fall or winter, not the dog days of summer.
But what if your love of dark beer knows no bounds, and you don't want to drink a beer you can see through no matter how hot it gets? The answer to your dilemma is Negra Modelo, a Mexican dark lager. Negra Modelo is a beer you can drink comfortably when it's a 100 degrees outside, but it's pleasantly dark in color and has a more interesting flavor than Corona or Dos Equis.
It's not a stout, but if you're sitting there drinking a stout in that kind of heat, you need to learn about some of the other beers in the world! If you've ever found yourself dragging your bloated carcass down the street in the blazing sun, wishing you had drunk something other than Guinness with your lunch, then you'll know what I'm talking about. If you're one of those Guinness fanatics who will drink nothing else no matter what the conditions, then you will surely disregard this. But don't say I didn't warn you!