Thanks so much for your suggestions. As a followup I could add: Perhaps I didn't have the gas cap on tightly enough when I filled it 3 weeks prior. The tank was close to empty when the check engine light came on. I filled the tank and drove to my mechanic who downloaded the code and reset the light. On the next day I drove the car about 200 miles and the check engine light stayed off.

I haven't driven it yet during cold/wet to see if I get a rerun of the window fogging conditions. As an answer to some of the questions, the HVAC system is the 'standard' manual climate control setup -- twist-dial the temp, twist-dial the airflow distribution. While I had the a.c. on, I didn't have the recirculation turned on. The outside air rolling wheel was turned off.

I've got several packs of replacement vacuum line elbows which I bought from IPD years ago; I guess it's time to check out if any should be replaced.

Rob K.