My wife and I visited Jungfrau in August 2017. We managed to luck out with our visit, with super clear skies and reasonable temperatures both in the valley and up top. Given the prices and the crowds, I would strongly recommend purchasing the "Good Morning" ticket, which offers a substantial discount (down to about 120 CHF per person). You need to be on one of the first two trains up in the morning (departing Grindelweld at 7:25 or 7:40), and then descend again from the mountain by around 1:30pm.

Staying in Grindelweld, we managed to make it up on the first train, skipped over the first parts of the tour and were on the first elevator to the top of the observatory, meaning that we had it entirely to ourselves for about 10 minutes. Fantastic! Though it did fill up with obnoxious tour groups after about 45 minutes.

I would also strongly recommend doing the glacier walk out to the far viewpoint, as you get a completely different view of the area. Although it's shown as 45 minutes, it's probably closer to an hour unless you're an experienced snow walker. We took an hour, though our miniature dachshund (teckel) slowed us down quite a bit!

All in all, a great day and we were very glad of doing the research to get the cheaper tickets, making it up before some of the crowds, and descending early afternoon for a rest and a well deserved beer.

See below for my full video review!