Nevando means "snowing". This word is the key to the song's incredibly creative and emotional metaphor, which is even hinted at in the title, "Barranquilla Below Zero".
Barranquilla is a famously hot, tropical city on the coast of Colombia where it never snows. The singer says, "Desde que te fuiste en Barranquilla está nevando" (Since you left, it's been snowing in Barranquilla), to paint a surreal picture of how cold and empty his world has become without his love. It’s a powerful and memorable way to describe the chill of a broken heart.
This song kicks off with one of the most dramatic breakup lines ever: "Desde que te fuiste en Barranquilla está nevando" (Since you left, it's snowing in Barranquilla). Barranquilla is a hot, tropical city in Colombia, so he's saying the world has turned completely upside down and cold without his ex. Everything has lost its color, with rainbows appearing in black and white, and love becoming as rare as "contrabando" (contraband). The singers are full of regret, wishing they could turn back the clock to stop her from leaving and admitting it's all their fault.
They spend the rest of the song alternating between begging her to come back and remembering how amazing she is. He calls her a "pintura de Picasso" (a Picasso painting) and an "obra de arte" (a work of art). There's a great piece of advice for everyone listening: "Si tienes una mujer buena, cuídala y respétala / Si no vas a perderla como la perdí yo" (If you have a good woman, take care of her and respect her / Or you'll lose her like I lost her). It's a song about a massive, world-altering heartbreak and the desperate hope of fixing a mistake.