Wait can someone tell me

[The Archduke of Kiwis]

How does someone know they have a fever??  

[Emo_Like_A_Dinosaur]

Cheer up and dry your damp eyes and tell me when it rains

.+
If your temperature is above normal.
+.

And I'll blend up that rainbow above you and shoot it through your veins

 

[Eat My Porn Flakes]

By using a thermometer or taking your hands to your head and if It's hot, bingo. Fever.  

[karzlee]

I define fever as anything over 99 degrees F, but that's because my normal temp is around 97.
Most people define a fever as being anything over 101.
Although 100-101 is also sometimes considered a "Low Grade fever"
The average normal body temperature is 98.6
Hope this is helpful.