Question: Which term is the correct one in British English for descring degrees in Celcius scale?

I've always refered to it with minus, for instance: In Siberia there are minus 50 degrees. But today I saw [this](https://youtu.be/Fz4ZMLsPzqM) video in which the author is saying "negative 50" when refering to Celcius degrees.

So, in short, I'd love to know wheather in British English we should say negative 50 degrees or minus 50 degrees.

Answer: 
"It is minus fifty" (not there are minus fifty)

Saying "negative fifty" is a slightly more scientific alternative. Both "minus" and "negative" are used.
You can have below-zero temperatures in Fahrenheit as well as Celsius.

The usual spelling of the C degree name is Celsius. That's how the Swedish scientist (Anders Celsius) who invented the C scale spelled his name.

0 degrees F is minus 17.78 degrees Celsius, so 'sub zero temperatures' in Fahrenheit countries (the US and Liberia) is seriously cold. I don't think it gets that cold in Liberia. The lowest recorded temperature in Monrovia is 59.0°F (15°C), Minus 40 degrees is the same temperature in Celsius and Fahrenheit.