Sure! Here are the completed sentences with the correct forms of the words in parentheses:

1. Tomorrow, it will be **cloudy** and cool.
2. The substance is toxic and **flammable**.
3. A bomb **exploded** in a crowded metro station this morning, killing five people.
4. It was a cold and **frosty** morning.
5. It will be a long, slow and tedious process requiring patience and **constancy** of purpose.
6. She was found alive but **unconscious**.
7. As she fell, she hit her head and lost **consciousness** for several minutes.
8. The weather continued to be **rainy**.
9. I was very **conscious** of the fact that I had to make a good impression.
10. The English language is constantly changing, slowed down by the **shower** outbreak.
11. The tree had come down on the day of the big **storm**.
12. When we arrived in Ha Noi, it was warm and **sunny**.
13. Low blood sugar, if not treated, can cause **unconsciousness**.
14. It's raining heavily.

Feel free to ask if you need more assistance!