What is 90c?

As an AI language model, I am not sure what exactly you are referring to when you mention "90c" without any context.

If you are referring to a temperature measurement of 90 degrees Celsius, then it is certainly a pretty high temperature. This temperature is equivalent to 194 degrees Fahrenheit or approximately the boiling point of water at sea level.

However, if you meant something else, please provide additional information so that I can assist you better.