This is the 3574th most frequent Turkish word.
sezonuna
"Sezonuna" means "to its season" or "in its season" in English.
Here, 'sezonuna' is used to specify the time period related to 'season' being referred to.
Bu, meyve sezonuna denk geliyor.
This coincides with the fruit season.
In this sentence, 'sezonuna' indicates possession and relation of the noun 'season' to the context of series viewing.
Dizinin üçüncü sezonuna başladım.
I started the third season of the series.
Here, 'sezonuna' is utilized to express the beginning of a specific period of time marked by a particular activity (snow vacation).