I had this exact same problem with my '97 Tbird, and the problem was a very simple, but not obvious one (at least in my case).
If you live in an area where you have a lot of cottonwood, for example, but even just collection of airborne dust and debris will, over time, clog the vanes on the radiator. It's not obvious when you look at it, because this debris (especially cottonwood) packs itself well into those little vents.
In a SAFE condition (including being sure that the fan won't kick in), the solution was to CAREFULLY (so as not to damage the radiator vanes) spray the radiator from the rear side forward. This will blow out whatever debris is packed into the radiator and blocking air flow.
Once I did that, my temperature under climb or load went WAY down and right into the middle of the normal range.
You may still have other problems, such as a thermostat problem or an internally clogged radiator, but this is a cheap (free) option to check out.
It worked absolute wonders for me.
(BTW: climbing a hill could run my temp up into the red after as little as one block, depending on the grade, but would drop to normal a block later...) | 
