In Celsius -4oC
In Fahrenheit = -4oF
The Fahrenheit temperature is much much colder than the Celsius One. You must dress very much for winter in -4C. I live in a country where - 30 is common during the winter the odd year we get a couple of days that are - 40 in either scale. The telephone wires sing when it gets that low. That's how you know what the temperature is without looking at a thermometer.