The car is a '91 Olds 88.

Whenever the temps drop to just above freezing and the car is driven for a while in rain or on wet roads, the power door locks stop working and then they start working again after the car has been parked for a little while. Whether I press the lock button to lock or unlock the doors, absolutely nothing happens.

Has anyone seen something like this before? This only happens in a combination of close to freezing temps and the car being exposed to wet roads.

How "Absolutely Nothing" is that? Do you hear any "clicking" at all from inside the car? Does this happen with either the driver AND the passenger door lock switches? I had a problem with my driver'* side switch and it turned out to be a stuck contact underneath the switch plate.

No clicking. Both switches act the same way.

Once the car sits for a little while after being driven in the conditions described, everything goes back to normal.

Do you have a module that controls the locks?

The cold and moisture in the air sounds like maybe such a module is being exposed to the moisture in the air somehow...

PDL problems do strange things, I have heard worse.

YET, in diagrams, it just shows a very simple circuit for the PDL and switches.