Driving from Lake Constance to Interlaken
 

Will we need snow chains in late December? Staying at a hotel near Interlaken West Train station. Many thanks.

Not likely - not if you take the expressways via Aarau-Solothurn-Bern-Thun, it would be a huge fluke along that route.

But if you choose the much more scenic route via Zug-Luzern-Meiringen, there is a bit more of a likelihood of snow, but rarely a need for chains.

Interlaken is not very high up, it is the gateway to the mountains, but itself it is down below, between the two lakes, and the road to there is pretty flat.

Konstanz and its lake (which is called Bodensee in the local language) are also not elevated.

Be aware of the need for the "vignette" - a roadtax sticker that it mandatory as soon as you enter an Autobahn (expressway). Your rental car should really have it affixed already (it is not transferable). Make sure you check.

A dreaded word, but good to know: "Stau" - it means congestion, to the point of stillstand, and it is a frequent occurence, so if you see it posted, relax...

Thanks for the information - the car hire company did not supply winter tyres or chains as requested - our fault we did not check as we picked the car up in Bergamo a couple of weeks ago.

If you are already in Switzerland, I would definetely try to get winter tires for your car asap.
You will probably forfeit your insurance if you get into an accident with summer tires.

You don't need chains to drive in/on snow -- that's what winter tires are made for.
Roads which require chains are signposted.

Unfortunately we have checked again with the car rental firm - we rented in Italy and are returning car to Paris mid January - if we do not keep the car we lose our money. We are trying to organise snow chains through the car rental company to pick up in Paris - any other advice?

Hope for a mild winter until January.

Sorry, I do not mean to be sarcastic, since your screen name suggests that you are maybe not used to winter (i.e. snow, ice, slush etc) driving.

Summer tires in combination with chains can never substitute winter tires.

Chains are useful for driving in the mountains in winter - but usually (except maybe right after a heavy snow storm) not needed except on steep roads, like mountain pass roads with no regular winter closure. Regular roads are either plowed and de-iced, or get some gravel on a solid snow layer.
What you will encounter are icy stretches of road or bridges, esp. around dawn or dusk, mud or slush from anti-icing agents etc.
Nothing that chains are made for or help against. And, by the way, I think also CH has a speed limit of 50kmh once you drive with chains.

I do not want to sound like your mother, but driving around Switzerland in late December with summer tires is calling for real trouble, IMO.