What is the coldest letter in the alphabet?

The concept of a "coldest letter" in the alphabet is subjective and not based on any scientific or mathematical principle. However, if we were to consider the coldest-sounding letter based on phonetics, some may argue that the letter "Z" could be perceived as cold due to its sharp, hissing sound. Ultimately, this is a matter of personal interpretation and not a universally accepted concept in linguistics or any other field.