The phrase due to functions as an adjective, whereas because of functions as an adverb.
Recall that adverbs modify verbs, adjectives, and other adverbs and answer questions such as when, where, how, to what extent, and why.
Steve walked slowly down the street. “Slowly” tells us how Steve (subject) walked (verb); “down the street” is a prepositional phrase that tells us where he walked. “Steve walked” can stand on its own, but the extra words provide additional information about Steve’s action.
Adjectives modify (or describe) nouns and pronouns, so if we want more information about Steve, rather than about his walking, we look to adjectives.
Steve was ecstatic. (“Ecstatic” is an adjective.)
In the USDA notice above, the phrase that modifies closed (an adjective) is there to explain why the facility is closed; therefore, an adverbial phrase (because of) is needed.
The closure was due to bad weather. (The adjectival phrase due to bad weather modifies the noun closure. I could choose other adjectives to describe the closure: The closure was brief. Or: The closure was unexpected. Brief and unexpected are adjectives.)
The school is closed because of bad weather. (“The school is closed” would be a complete sentence, but the additional information explains why the school is closed. because of is part of an adverbial phrase that modifies an adjective (closed). The sentence could be rewritten as: Because of bad weather, the school is closed.)
Breaking a sentence into its basic components can sometimes help you see the functions of different parts more clearly:
This facility is closed due to funding. X
Here, facility (noun) is the subject, is is the verb, and closed is an adjective modifying facility. The rest of the sentence explains “why” the facility is closed; thus, an adverbial phrase (because of) is needed.
The sign should read:
This U.S. Department of Agriculture facility is currently closed because of the lapse in federal government funding. ✓
The closure is due to Congressional inaction. (The phrase due to Congressional inaction is modifying the subject (closure), so it functions as an adjective.)
The following sentence could stand on its own:
The park is closed.
We can add additional information to it:
The park is closed because of inadequate funding. (Because of explains why the park is closed (i.e., it modifies the adjective closed).)
The closure is due to inadequate funding. (Compare: “The closure is temporary.” temporary is an adjective.)
In casual conversation, we are more likely to say because of (unless we are speaking of arrivals and departures: Scott is due to arrive in one hour.)
I left because of his insults.
I was late for work because of the storm.
In written communications, due to can seem more formal.
I was late for work due to unforeseen circumstances. X
The purpose of the phrase “due to unforeseen circumstances” is to explain why I was late; thus, because of is the correct choice.
If formality is appropriate, correct usage is essential!
Takeaway: Don’t worry if you can’t remember when to use due to and when to use because of. If you know that the two often get confused in people’s minds (perhaps in yours, too), then when you are writing or editing one of these phrases, you can take a moment to refresh your memory before finalizing your message or document.
By reading things that are well written (and following blogs such as this one!) you are expanding your knowledge base and improving your ability to spot problems. If you find a problem, you have an opportunity to fix it!