Those folks must live a lot closer to the Arctic Circle than you and I.

My stabilization temp ('82 300D) is close to 85 C. On a 100 F day, it will approach 100 C in stop & go traffic with the a/c (and aux fan) running. Like you, I recently replaced my radiator due to a leaking upper seam and saw no material difference in operating temps. The tubes in the original radiator were very clean. My water pump and fan clutch replaced recently.