"It had started to snow by 10 a.m. yesterday." vs "It started to snow by 10 a.m. yesterday." [closed]

It had started to snow by 10 a.m. yesterday.

Yes, this sentence is grammatical and natural.

First, we must acknowledge that the past perfect ("had started") is distinct from the past indicative ("started").

"Had started" is the past perfect form of the verb "to start." Past perfect is typically used to describe an event that occurred and ended before another one (which also occurred in the past). There are other uses for this tense, but this is the one that is applicable to your situation.

Let’s look at why saying “had started” is likely the best tense to use in this situation. As I wrote above, the past perfect describes an event that occurred and ended before another event in the past. In this case, we want to say that the beginning of the snow falling came before 10 a.m. yesterday. This means that our first event (snow starting to fall) starts and ends before our second event (10 a.m. yesterday). When I say that the first event “ends,” remember that the event is the snow starting to fall; therefore, the snow has already started to fall before 10 a.m. yesterday.

The past indicative tense (also known as the “simple past”) is typically used to describe actions that were completed at a specified time. There are other uses, but this is the one that is applicable to your situation. Although the action (snow beginning to fall) was completed in the past, it’s time is unspecified. We know it happened before 10 a.m. yesterday, but we don’t know exactly when; therefore, the past indicative tense would be incorrect in this situation.