The Jungfraujoch is accessible all year round by the Jungfrau Railways.
Possible routes:
Interlaken Ost – Grindelwald Terminal – Eigergletscher – Jungfraujoch
Interlaken Ost – Lauterbrunnen – Kleine Scheidegg – Jungfraujoch
Travel time:
From Interlaken Ost to Jungfraujoch by Grindelwald Terminal/Eigergletscher (with the Eiger Express gondola cableway): about 1.5 hours.
From Interlaken Ost to Jungfraujoch by Lauterbrunnen/Kleine Scheidegg/Eigergletscher (by railway): about 2 hours.
Parking:
The closest parking possibilities are at the railway stations of Grindelwald Grund/Grindelwald Terminal and Lauterbrunnen.
Map of the Jungfrauregion with public transports. (click to enlarge)