Since due to
is an adjective, it needs a noun or pronoun to modify. To assure this functioning, the safest place for due to
is after a form of the verb to be because there it is always serves as an adjective: "The cancellation was due to bad weather" (due to
modifies the noun cancellation).
The most dangerous placement of due to
is at the head of a sentence. In "Due to rain" or in "Due to the lateness of the hour" or "Due to a cold I was unable to attend", due to
is treated as an adverbial phrase. this is a misuse. A test to determine whether due to
is being used correctly is to replace it with "caused by" or "attributed to", which is what due to
means. If the replacements make sense, due to
is correctly used, as it is in "The explosion was due to [caused by or attributed to] carelessness."