Breakdown of В сильный мороз даже собака не хочет долго гулять и начинает дрожать у двери.
Questions & Answers about В сильный мороз даже собака не хочет долго гулять и начинает дрожать у двери.
Мороз is in the accusative case here, and сильный agrees with it.
This is a common Russian pattern:
- в + accusative can be used in time or condition expressions
- в сильный мороз means something like in severe frost / when it is very cold
Why does сильный look the same as nominative? Because for a masculine inanimate noun, the accusative singular has the same form as the nominative:
- nominative: сильный мороз
- accusative: в сильный мороз
So the form does change by case grammatically, but in this specific type of noun, it happens to look identical.
Also, this phrase is idiomatic: Russian often says в мороз, в жару, в холод, etc. to describe weather conditions.