Year Round
All Year, Whole Year, Throughout The Year
adverb, noun
The year middle sounds like it should be something like "the middle of the year," but it's not. Think of something that happens in the middle of the year and then all other parts of the year. It's just referring to everything within this year, which is how we get year round.
This is a jukugo word, which usually means on'yomi readings for the kanji. If you know the readings of your kanji you'll know how to read this as well. 中 does have a strange reading, though, which is じゅう. This is basically just ちゅう changing to ぢゅう, but since ぢ is very rare it just switches to じ and you end up with じゅう. That's called rendaku.
年中いそがしい
busy all year round
年中ハッピー
happy all year round
年中あたたかい
warm all year round
お父さんは年中外にいる。
Dad is outside all year round.
年中うるさくて、すみません。
I'm sorry for being noisy all year.
この町は年中あたたかいですよ。
This town is warm throughout the year.