Is a temperature of 99.4 considered a fever?

Typically not. Usually fever is considered 100.5 or greater.
In isolation, no.... Outside the neonatal period, or in special circumstances like hematopoietic stem cell transplant, the definition of fever is a single temperature of 101 or two temperatures of 100.4 or more separated in time by 30 minutes or more. While most believe that 98.6 is normal and other temps are not, this is not the case. Temperature actually fluctuates through a range during the day.