Here are the completed sentences:
- There was a nice breeze so we could sail across the lake.
- The first raindrop fell at nine and by ten it was raining hard.
- He ran inside when he heard the thunder.
- It was only a little shower so we didn't get very wet.
- The lightning hit a tree and started a fire.
- You can't catch a snowflake - it turns into water in your hand.