The correct answer is - D. temperature.
When a meteorologist says that it is hot or cold, than he/she is describing the temperature. Even though it is not a precise information, people can approximately understand what the meteorologist means when he/she puts the information in a descriptive manner.
The perception of hot and cold varies a lot from place to place, so it is subjective to a certain place, because the people living around the Equator will consider the weather to be hot if the temperatures are going 40 or 45 C degrees, while the people living around the Arctic circle will consider a temperature of around 20 to 25 degrees to be hot.