1. It's a little chilly. 2. It's freezing. (= extremely cold) 3. The temperature's dropping. 4. Make sure to bundle up. (bundle up = put on warm clothes for protection against the cold) 5. We're expecting some winter weather. (winter weather = snow, hail, sleet, ice, etc.)
This will give you more control and enough time to tie up loose ends. Knowing that you have control over the situation, will ensure greater success. This will also avoid nervousness and unnecessary exam jitters.