On further reflection, shouldn't the rear fan kick in and out from slow to fast speed as the radiator gets hotter and cooler? It seems that once it goes on to fast at the moment it stays there, I don't think this is right.
On the V6 - and 2.2 will be broadly similar, except less fans - the slow speed fan comes on at just over mid-point on the gauge (so around 96C on prefacelifts, and 87C on facelifts - the temps are actually the same if measured, but the gauge markings on the FL are lower for reasons only GM knows).
The high speed fan comes on as the needle approaches the upper marking on the gauge - so around 98/99C on PFL, and 88C on FL. It's rare to hit these conditions except in hot weather after a run.
(All assuming A/C off, if on, obviously the slow fans come on anyway)
HTH