Do you have your full fan shroud installed?
It seems like it's normal (or at least common) for them to get above the normal range when climbing in warm weather...yours would be the 5th Montero out of 5 that tends to do this, including mine, but I don't have a fan shroud so that's why I was curious. In other vehicles I've owned, no shroud = overheating. It makes a significant difference in the amount of air the fan can pull through the radiator. The vented hood made a noticeable difference and seemed to offset the missing shroud.
Anyhow, do you have plans to upgrade? My solution is a larger electric fan...just gotta get off my butt and install it!