Brrrr... It's Cold: talking about temperature

Update 2017-02-25: Updated vocabulary dictionary links.

A thermometer with two scales for showing the temperature in both Celsius and Fahrenheit.

Many of my students in China are mentioning how cold it is there right now, but are having issues with the vocabulary for describing the temperature (how hot or cold it is).

In this article, I will try to clear up how to speak about the temperature of the weather. I will write temperatures and numbers as words to show how they are spoken, e.g. "minus fifteen degrees Celsius". And I'll write the digits and symbols in brackets, e.g. "(-15°C)" to make clear exactly what the temperature is and to show how they are usually written. 

Firstly, °. That symbol is pronounced "degrees" (UNIT). English speakers talk about temperature both with AND without this word.

• The weather forecast said it will be only two degrees (2°) today.
•  The weather forecast said it will be only two (2°) today. 

Both those sentences are OK (as the context makes it clear that the number refers to the temperature).

Secondly, there are two measuring systems for temperature: Celsius / Centigrade (abbreviated as C) and Fahrenheit  (abbreviated as F) . In most English-speaking countries, we now use Celsius. But in the United States ( and in the recent past in Britain and others) they still use Fahrenheit. So if you're speaking with an American, make clear which measuring system you're using.

• It's nine degrees Celsius (9°C) in Shanghai today. That's about forty-eight degrees Fahrenheit (48°F).

Most weather websites allow you to change between °C and °F, like the BBC Weather site. There are also websites dedicated to conversions between measuring systems, like Metric-conversions.org.

Thirdly, when it gets really cold, we can use words like  "minus" and  "below" in combination with numbers referring to the temperature.

"Minus" (#2) before a number refers to temperatures below 0°. 

• In Jilin today, it's minus fifteen degrees Celsius (-15°C). That's five degrees Fahrenheit (5°F).

"Below" (#2) / "below zero" after a number also refers to temperatures below 0°.

• In Jilin today, it's fifteen below (-15°C). That's five degrees above zero in Fahrenheit (5°F). But tonight it'll reach twenty-nine below (-29°C). That's twenty below (-20°F) in Fahrenheit.

Fourthly, "freezing" refers to the temperature at which water becomes ice. In Celsius, that's 0°. But in Fahrenheit, that's 32°.  But English-speakers also use "freezing" to mean "very cold", regardless of the actual numbers of the temperature.

• Newsreader: "Tonight, temperatures will reach freezing in northern parts of the country".
  

From the technical context, "freezing" here means 0°C / 32°F.

• Friend: "Wow, it's freezing. I need some hot coffee to warm up."
  

From the casual context, "freezing" here means "very cold": it could be at OR above OR below 0°C, what matters is that the speaker feels very cold.

Finally, "brrr..." is a sound English speakers make to express that they feel very cold.

"Brrrrrrr...."