Sentences 1) and 2) are OK. Sentence 1), without the definite determiner "the," is hypothetical/theoretical; it refers to any or every closing. Sentence 2), with definite determiner "the," refers to a real, specific closing that both the writer and the reader know about. The simple present "causes" in sentence 2) makes it sound as if the c losing of the factory is a habit, something that happens perhaps every summer.
"Closure" is grammatical but somewhat awkward in this context. Don't use it.
This is a good question.