Nimbostratus clouds - Met Office
Learn about nimbostratus clouds, dark, grey, featureless layers of cloud that produce continuous rain or snow. Find out how they form, what weather they are associated with and how they are categorised.
and the contradiction
"dark, grey, featureless layers of cloud that produce continuous rain or snow"
vs
"la parure des flammes ... les teintes de jais et d’onyx qui rivalisaient avec la couleur du ciel nocturne."
Strange choice of name for a city ...
BTW I would stay clear of this site
https://www.calameo.com. If you are forced to first download and run an .exe file (originating from an advertisement website) before downloading the .pdf of the book, it definitely does not smell of roses.