Learn Hardcore Korean: 1wolgwa 2woreun gyeourieoseo nalssiga chuwoyo. - January and February are winter months, so the weather is cold.

In Korean 1월 is pronounced il-wol and 2월 as i-wol. The particle 과 means and but follows nouns ending in a consonant sound. Since both 1월 and 2월 end in ㄹ (a consonant), we use 과 to link them and say January and February.

What role does 은 play in 1월과 2월은?

은 is the topic marker. By saying 1월과 2월은, you are signaling that the sentence is about January and February in general—sort of like starting “As for January and February…”

What does 겨울이어서 mean in this sentence?

It combines 겨울이다 (to be winter) with the connective ending -어서 (indicating cause). Together 겨울이어서 means Because it is winter or Since it’s winter.

I’ve also seen 겨울이라서 used. Are both forms correct?

Yes. Both 겨울이어서 and 겨울이라서 come from 이다 + -아서/어서 and mean the same thing (“because/since it’s winter”). -이라서 is more common in spoken Korean, but -이어서 is perfectly acceptable.

Why is 날씨가 marked with 가 instead of 는?

The particle 가 marks the grammatical subject. In 날씨가 추워요, 날씨 is the subject (“the weather is cold”). If you used 는, you’d be making 날씨 the topic instead, which shifts the nuance or sets up a contrast.

Why is 춥다 changed to 추워요 here?

춥다 is the dictionary/plain form meaning “to be cold.” In polite speech you take the stem 춥-, apply vowel harmony to get 추워-, then add -요, resulting in 추워요.

Could you use -기 때문에 instead of -아서/어서 to express the reason?

Yes. You could say 1월과 2월은 겨울이기 때문에 날씨가 추워요. The -기 때문에 form is a bit more formal and often used in writing, whereas -아서/어서 is common in everyday conversation.