June, July and August: warmest weather (highs 18-22°C), long daylight (up to 17 hours), and the town is fully open – all museums, outdoor cafes, and…
May and September: temperatures still pleasant (10-15°C in May, 12-16°C in September), hotel rates drop 15-25%, crowds thin out,…
Go in June or September for the best balance of decent weather, open sites, and sane prices.