How do we grade fever?

Low grade and high: Low gr. Fever is -> 99 to 101f approx. Anything more than is high fever. But in the high fever , from101 to 104 , we treat as high feverand is common but more than 104 is given a terminology called hyperthermia which is a medical emergency. Fever in children and elderly, immunocompromised people like -- with diabtes, cancers, even mild fever is significant , and limit -100.4 instead of 101 to trt