will be visiting switzerland / jungfrau in October 2016. What dress precaution required for us there.
Depends on high up you want to go. You can take the train up the Jungfraujoch. That's almost 3500 m of altitude and hence it's cold, even in Summer. Means: below freezing even in August. Check out http://www.jungfrau.ch/en/tourism/destinations/jungfraujoch-top-of-europe/weather/
Prepare for ice, snow, and significant sub-zero temperatures. The lower you stay the warmer it will be.