Gloomy, even. Not to be confused with cartilaginous. One of those words that looks nothing like its meaning, in part because English doesn't have other words from the root: that being Latin cālīginōsus, misty/obscure, from cālīgō, darkness, mist. (This was borrowed in the 1540s either directly or via French caligineux, our records aren't clear on the matter.)
By the time I reached Castro Street, the air had thickened to caliginous and I'd turned up my collar.