Learn Swedish: Visst blir det kallt på natten, men en avskild skog är charmig.

It can mean "certainly", but in the visst [X], men [Y] structure it acts as a concession, meaning "admittedly" or "sure". It acknowledges a drawback before introducing the positive counterpoint: "Sure, it gets cold..., but..."

Why is the word order visst blir det instead of visst det blir?

This is a great reminder of the Swedish V2 (verb-second) rule. Because the adverb visst takes the first position in the clause, the main verb blir must come immediately after it in the second position, pushing the subject det to the third spot.

Why do we use the verb blir instead of är here?

While you could say är (is), using blir (becomes/gets) emphasizes the transition. It implies that as the day ends, the temperature drops and it gets cold.

Why is natten in the definite form in the phrase på natten?

When talking about parts of the day in a general or habitual sense (like "at night" or "during the night"), Swedish pairs the preposition på with the definite form of the noun.

What type of word is avskild?