The Bregenz Festival runs every July and August, and this is when the town is at its most animated — and most expensive. Book accommodation well in advance if you plan to attend performances. Even if you are not going to the opera, the summer months bring warm weather, swimming in the lake, and the full buzz of the lakeside.
Spring and early autumn are quieter and pleasant, with mild temperatures and fewer crowds. The cultural programme at the Landestheater and the museums runs year-round (except July and August, when the Festival dominates). Winter is cool and sometimes grey, but the Pfänder gets snow, and the town takes on a calm, local character that summer visitors rarely see.
If you are combining Bregenz with a broader Lake Constance trip, summer is ideal for boat connections and cycling. The lake temperature reaches around 23°C in July and August — warm enough for extended swimming.