It is set so that pure water freezes at zero degrees Celsius and boils at one hundred degrees Celsius. And with 100 degrees between those points, we can specify temperatures using 1 or 2 digit positive numbers. When the temperature is negative, i.e. below 0 °C, then we know that it is so cold that water will freeze.
In this way, can you have a negative Celsius temperature?
At zero kelvin (minus 273 degrees Celsius) the particles stop moving and all disorder disappears. Thus, nothing can be colder than absolute zero on the Kelvin scale. Physicists have now created an atomic gas in the laboratory that nonetheless has negative Kelvin values.
Can temperature be lower than absolute zero?
At the physically impossible-to-reach temperature of zero kelvin, or minus 459.67 degrees Fahrenheit (minus 273.15 degrees Celsius), atoms would stop moving. As such, nothing can be colder than absolute zero on the Kelvin scale.