Final answer:
The correct verb to complete the sentence is 'está.' It is used to describe the current state of the weather.
Step-by-step explanation:
The correct verb to complete the sentence is está.
The sentence says 'Hoy empieza el invierno y está nevando', which means 'Today winter begins and it is snowing.'
In this context, the verb 'estar' (to be) is used to describe the current state of the weather, indicating that it is snowing.
Learn more about Spanish verbs