Este invierno el clima [blank] muy frío. - "This winter the weather [blank] very cold.
Let's take a look at our options and see which one makes the most sense here:
hace = does
está = this, it is, is
tiene = it has
hay = there is/are
Answer:
Este invierno el clima está muy frío.
There is another way of phrasing this sentence using hace which makes just as much sense, but which translates slightly differently; that would be Este invierno hace mucho frío. As you can see, this sentence uses mucho instead of muy, which changes the literal translation from "This winter the weather is very cold" to "This winter it does a lot of cold", which seems to not make sense in English, but makes perfect sense in Spanish. Anyway, the answer to your question is está.
Hope this helps!