NB. This event is in Château d'Oex, not Lausanne

International Balloon Festival - official blurb

"Absolutely unique in an alpine environment, the Night Glow nighttime sound and light show is a highlight of the International Balloon Festival. About twenty hot-air balloons, paragliders, members of the Swiss Ski School and fireworks experts illuminate the night of Château-d'Oex for a performance that makes a lasting impression. To make the most of this show, spectators can take their seats on Temple Hill and on the southern part of the football field.

Show subject to weather conditions. Decision communicated on Thursday 30 January at 1 p.m."

I went a few years ago and it's absolutely stunning so very much worth returning or going for the first time!

We would take the train up there - the MOB from Montreux station - at 17.32 arriving in Chateau d'Oex at 18.32 or possibly the earlier one at 16.44 arriving 17.44. The fare is 10.10CHF each way with the 1/2 card reduction. I don't know if we have to reserve as the trains get very busy that evening, so I'll enquire depending on the response to this proposal.

I'm sure there are stands there where we can get snacks & drinks. No doubt there'll be plenty of vin chaud.

As stated above, this event is weather dependent.