I observed this when letting the heated car idle with A/C off and ambient temperature of 30C.
To observe the heat, I took off the hose on top of the coolant tank that feeds water back into the tank, let it flow down on the ground while I make sure the tank stays filled.
-Temperature shows 88C. Fan Off.
-Temperature showing 95C, but clearly the water is steaming and at boiling point, Fan starts at perhaps Step 2
-The fan started, but it is too late, temperature keeps rising and water starts boiling heavily
I had to drain the air out of the system after this and continue doing it a couple of loops. I don't experience the overheating issue lately.
My friends tell me this is normal behavior.
Except it can be improved with this:
A) My fan may be too weak, needs re-work (40$ at a specialist)
B) I saw a hose that is bent at the front of the engine. Shady work from previous owner. (0.1$ DIY)
C) another hose at the front of the engine is probably leaking, rusty residue around the joints. (0.2$ DIY)
D) My radiator is not air-tight, rusty ($$$)
I'll do A,B,C later this month.