"What is this a sign of?"
Could be anything from your new MLPS to TSS to water getting into the wiring to the O2 sensor.
"Do I have electrical problems. Is this a sign of frayed wires getting weat."
Maybe.
"How do I describe this problem to a tech guy when it occurs sometimes only in the rain?"
Don't.
Last Friday, I drove in the pouring rain for 5 hours -200 miles or so (field work day, figures

). Got a CEL P0136 the next day I drove it (Monday). Attributed it to rain getting in my connector for the O2. Turned it off and didn't do anything. It is Thursday and 100 miles later and CEL is not back yet. My suggestion; if you want to troubleshoot, use a garden hose and spray the top of the Contour for a while and see if any water gets to the engine bay area.
Now, if you are still under the 10 year/100K wiring harness warranty, then it might be good to have Ford check the wiring harness. Good luck.
Edit. You may want to just retrieve the intermittent code if it is still there with a paper clip. I will probably duct tape the connector for my O2 sensor (as well as more tape over the MILeliminator

).