You are probably experiencing a power steering whine in cold temps < 60F, which goes away as the engine compartment gets warm. The culprit is the o-ring on the PS pump inlet pipe. The o-ring has become glazed & lost its original elasticity so its contracting more than spec and allowing air to enter the pump when the temps drop. The fix is simple, replace the o-ring.

Stuff some rags under the power steering pump, remove the hose on the front side of the pump (towards the bumper.) Remove the single 10mm bolt directly below the hose nipple. Give it a tug and the nipple will be separated from the pump. The old O-ring is stuck in the pump but it can be removed with a screwdriver and clean up the surface with a rag.

If you have a leaking power steering pump, dont just replace your pump. These orings are more than likely the fix!! Buy this to fix that problem instead of wasting hundreds of dollars on another pump!!