''Was raining'' helps to set the stage for what happens next. It helps to describe the scene. It uses the helping verb (''was'') with the present participle (''raining'').
Remember, the past progressive tense uses this format:
- I was + ing verb
- He was + ing verb
- She was +ing verb
- It was + ing verb
- They were + ing verb
Examples of ''ing verbs'' or present participle verbs include:
- Laughing
- Dancing
- Running
- Driving
- Waking
- Traveling
Important Uses
A lot of times, the past progressive tense describes something that was in the process of happening when another event occurred. It helps to paint the scene for when a specific incident occurred, or it can be used to describe an interrupted action.
I was doing my homework when the power went out.
''Was doing my homework'' describes what was in the process of happening when the single event, ''the power going out,'' occurred. The action of doing homework was interrupted by the power outage.
We were watching a movie when the doorbell rang.
Again, the doorbell ringing interrupted the continuous action in the past, ''watching a movie.''
It can also be used to describe two continuous events that were happening simultaneously:
In art class, they were painting while the other students were drawing.
The past progressive takes the same tense in the negative form:
We were not finished eating when they brought the check.
It also has the same tense in the question form:
- Were you sleeping when I knocked on the door?
- What were you doing last night?
Please note: they do not describe one single event in the past, like the verbs in these sentences:
- I stayed up late last night.
- She went to the mall last week.
- Last summer, their family went to Europe.