Ice Elementals are born where the Plane of Water meets and freezes against the Plane of Air. They have little need to interact with humanoids, but react poorly to those carrying fire or otherwise threatening their frigid privacy. In your campaign they might also be the result of magical experiments (the forced merging of air and water elementals) or servants of the powers of cold and winter.
Icebergs from the Plane of Water can spill out into the Plane of Air. (This is one source of many planar white dragons’ lairs.) Provided the currents keep the icebergs cold and close to the Plane of Water, the ice elementals that dwell there are not disturbed. But should their bergs drift too far or begin to melt, these ice elementals can become desperate to return home—and mortal adventurers’ airships are a too-rare and too-tempting target to ignore.
In academic circles, the most commonly witnessed form of ice elemental has generated comment. At the Elemental College of Auxenholt, the prevailing theory is a connection—perhaps a kind of impression from early summoning encounters—to some mortal serpentine race. Two rival scholars have taken sides on the issue—one posits primordial lamia matriarchs, the other the serpentfolk—and now both are establishing planar expeditions to prove their hypotheses.
For security, ice elementals on the Prime Plane sometimes ally with creatures that carry cold with them…but as most of these creatures are evil (such as yuki-onnas and various undead and fey creatures), ice elementals have earned a negative reputation by association. This bothers the amoral and otherwise isolationist elementals little. Also, over time they may begin to resemble creatures in their habitat, but only in form, not behavior—there are tales of ice elemental stags, crabs, and seals, athaches, and linnorms icewalking up sheer cliffs and even cavern ceilings.
—Pathfinder Bestiary 2 114–115
Gather round, children, as I tell you the tale of the Para-Elemental Plane of Ice:
Once Upon A Time, back in 1e and 2e, there were these things called Para- and Quasi- Elemental Planes. But that was before my time, and they vanished in 3.0. The End.
Now go fetch grandpa some bourbon.
(Actually, I like the idea of these interstitial planes—any excuse for more monsters is a good one—I just don’t know anything about them. (I vaguely remember a Dragon Magazine article—issue 174 maybe?—talking about the Quasi-Elemental Plane of Minerals as the source for ioun stones.) They seem to have lived on in the form of mephits and the various hybrid elementals.)