Summer Water Temp Baseline?

Umm, anywhere? I mean, if the radiator output is 230*F you’re pretty much boned but even if the inlet is 230 you’re not far off. If you’ve got a gauge reading 230*F you’re well on your way to overheating.

Exactly when the coolant boils depends on your coolant type/mix and radiator pressure, but if you’ve hit 230*F you’ve already gone well past the temperatures your cooling system is supposed to maintain, so it’s just a matter of time.