Nov 2, 2017 - 8:36 PM
in reply to Budwigboo
Keep in mind that high altitude hikes above about 1500 to 2000 meters will still be blocked by snow in the Jungfrau region, and that May is the middle of "low" season..between skiing and summer hiking. Many lifts ( cablecars) and mountain railroads do not start up until late May..typically around the 23rd. Some hotels and restaurants are closed. The "Summer" season starts around June 15th +/-.
Interlaken is at a much lower altitude than the mountain villages, and so it and the Lauterbrunnen Valley will probably be free of snow. The train to Jungfraujoch runs all year. Grindelwald, at 1000 meters above sea level is intermediate in altitude, and will likely be snow-free....or only have rmains of Winter on the ground.
Finally, and I think you realize this frnm your comments, if the Jungfrau and the high mountains are surrounded by clouds, a trip to the Jungfraujoch will be a very expensive way to see the insides of clouds.
The weather changes rapidly, so don't buy tickets until the night before. Or, in mid-May, there won't be serious lines. Buy tem the morning that they go up. Generally, clouds tend to gather around the Jungfrau in the afternoon more than in the morning. Check the weather with the tourist office and the hotel/inn/hostel before buying.