This is the 919th most frequent Finnish word.
talvena
"Talvena" means "in the winter" in English.
In this sentence, 'talvena' is used in the essive case to indicate the time period (winter) when an action occurred, emphasizing its role as the context for the verb 'satoi' (snowed).
Viime talvena lunta satoi paljon.
Last winter, it snowed a lot.
Here, 'talvena' is again in the essive case, but it metaphorically describes the state or period during which the subject was young and learning skiing, humorously personifying 'winter'.
Nuorena talvena hän oppi hiihtämään.
As a young winter, she learned to ski.
In this usage, 'talvena' denotes the current winter period where the action of 'matkustaneet' (traveled) took place.