Jungfrajoch

At the top it's very cold and usually windy. But most people hang-out in the enclosed observation decks. Reservations aren't possible on these mountain trains. All seats are first come first serve. The trains run frequently so overcrowding typically isn't a problem.

There is always snow on the top of the Jungfrau. In fact, you are looking out at a major glacier up there. It can be quite cold if you step outside the very large and nice facility. It's huge. It takes 2hrs to get up there from Lauterbrunnen with a train change in Kleine Scheidegg. The same journey time in reverse coming back down. It's a 22-minute trip from Interlaken Ost to Lauterbrunnen on the Jungfraubahn. There are several trains up to the Jungfraujoch each day. The first one out costs less. Also in the Lauterbrunnen station, and possibly from your hotel room, you can see live TV of the top of the mountain to check out the weather. Again, it's nice and cozy inside the building. It's a bit cold in the Ice Caves that you can walk through. One thing to watch out for is that occasionally, the second train up to the top from Kleine Scheidegg is fully booked for a tour group. We ran into this on our most recent trip up. Only a few of us got on the train. You find this out in the Lauterbrunnen station which we failed to do.

"...There are several trains up to the Jungfraujoch each day...." There are several trains each hour up to the Jungfrau. Tour groups get their own pre-arranged trains so you don't have to worry about them.

Just two comments. One do not even attempt to go to Jungfraujoch without first checking the weather, either in your hotel of if you are in Interlaken before top buy your tickets at Interlaken Ost station, there are screens there showing live pictures from the top.
Second, be prepared for all conditions at the top, I have sat in g;orious sunshire and sunbathed in the past. I have also onlyeen able to go as far as Wengen because of adverse weather conditions.