Está nublado.
Es-TAH noo-BLAH-doh
It is cloudy.
Most basic form
Está nublado hoy, qué gris.
Es-TAH noo-BLAH-doh oy, keh grees
It is cloudy today, how grey.
qué gris = how grey, common complaint
El cielo está plomizo, parece que va a llover.
El SYEH-lo Es-TAH plo-MEE-so, pah-REH-seh keh vah ah yo-VER
The sky is leaden, looks like it's going to rain.
plomizo = lead-colored, very native descriptor
More Spanish Weather Phrases