Matt & Shannon
Thanks for the clarification but I still don't see how you are traveling from Frankfurt and to Venice.
Is it by your own car, or a hire car, or train, or some other way. Upon that lies the answer.
Conventional wisdom is to take the train up to the Jungfraujoch in good clear weather, especially at the summit.
Usually the best weather at the summit is in the morning or around noon. Because of the air currents created as the earth warms up cloud begins to billow up and around the summit on many days after late morning, or there can be rain on any day. There are television screens in your hotel and in the train stations which show summit conditions.
If you arrive in the morning (all the way from Frankfurt - that's quite a long way?) and then check in and then paraglide and then start a 2 hour trip up the mountain, you may find that the best weather has left.