Stuck in traffic 340 got up to 220

Coolant will increase boiling point as does having it under a pressure cap.

from evans coolant site

About Pressurized Caps
Using a pressurized radiator cap can raise the system pressure and thus the coolant boiling point. A typical 1 Bar (14.5psi) pressure cap theoretically raises the boiling point of 50-50 coolant to 253°F,