How do you spell burr like its cold?

The spelling of "burr" doesn't change if it's cold. It's always spelled "burr."

However, if you're talking about the sensation of something being cold and prickly, you might use words like:

* Chilly

* Brrr (an onomatopoeia representing a shiver)

* Freezing

* Cold

Let me know if you were thinking of something else!