Oh, and mine is actually a May 2008 build.....suspicious

 

The last 6 digits of my vin jonboyb is 668219.

 

I am having the same issue. But its not really weather driven. It could be 70 out, and in 4th and sometimes even 3rd, I will get a 300-500 RPM variation at around 3500-4500 RPM. Has been doing this for about the last 10K miles. Car currently has 48860K on it. If I get time, I might take it into the dealer.

 

Mine has stopped doing it again with the recent change in weather down here. I want to leave it for a week when I take it and the 2 weeks I've scheduled so far have both tuned out to be above freezing so no use in taking it. If it's above 32 or so, it's not going to act up (other than a random slip in 5th every once and a while).

This is winter #3 of this happening.