Choosing locative preposition: Il fait froid __ montagne/ville/mer

Question

I am troubling with French locative prepositions.

When I want to talk about the overall environment of an area, like il fait froid/chaud, il y a du soleil, how can I know which preposition to use?

Il fait froid en montagne / ... à la montagne / dans la montagne.

Which is(/are) correct? What is the difference if any two of them are correct?

• I saw some on a random website say dans la montagne means "inside the mountain", which hardly make sense.
• en ville seems to be the most common collocation for ville, is dans la or à la also work if I am talking about the environment?
• How about the case of mer or nouns for other similar places?

Answer 1

Most alternatives are possible, sometimes with different meanings.

Il fait froid en montagne.
Il fait froid à la montagne.
Il fait froid dans la montagne.

Il fait froid en ville.
Il fait froid dans la ville.

Il fait froid en mer.
Il fait froid à la mer.
Il fait froid dans la mer.

En montagne and à la montagne tend to be more generic than dans la montagne. There is no problem with saying the latter which doesn't necessarily mean inside the mountain but more generally inside the area where the mountain is.

I don't list à la ville because it sounds like "rural French" to my ears.

Dans la mer means in the water, à la mer often means at the seaside while en mer means au large (offshore).