- Tom is busy today. He is cleaning his room.
- The weather is bad today. It is raining.
- He sometimes swims in summer.
- It sometimes rains in summer.
- It sometimes snows in December.
- She is working now.
- It is raining now.
- It is snowing now.
- She worked yesterday.
- It rained yesterday.
В предложениях с now используется Present Continuous, с sometimes — Present Simple, а с yesterday — Past Simple.