travelling from frankfurt to berchtesgaden

Have you thought about taking a train there? No one can really predict if there will be snow or not. But if there is, yes, you are required to have chains with you to drive. This would include driving from Munich to Berchtesgarten. A train to Munich only takes about 3 hours. If you fly, you need the same amount of time at least, if you include all the time at the airport for security, check in, etc. If you take a train, you get to see the lovely countryside, which is one of the reasons why are you coming to Europe isn't it?

I think it's early for snow as a rule but rules are made to be broken. If you rented a car at that time of the year in Salzburg, I would expect it to have mud and snow rated tires. Good tires are really all you need if drive carefully.

Maybe you could go into either Munich or Salzburg, then decide whether to rent or catch a train based on the actual weather conditions.

Two different times I had a car and could not go up the road to Berchtesgaden. Check the weather and call ahead to be sure the road is open before drive there.

I found this great website yesterday that will give you snow and weather conditions all year long, along with weather forecasts. It is mainly for ski areas, but still thought it was a useful site. Webcams were available on it too. Just type in where you want to go.
http://www.snow-forecast.com/resorts/Berchtesgadener-Land

Sally,
I just returned from Berchtesgaden, what a wonderful place to go!! If you do not have a hotel booked yet, please send me a PM and i will give you the name of the place we stayed. It was a fantastic B&B with great prices and location.