When should I visit Lyon, France, for the best experience?

Lyon's year has a summit no other French city can copy. On December 8, 1852, Lyonnais put candles — lumignons — in their windows to honour the Virgin Mary on the day her statue was finally installed on Fourvière hill after bad weather delayed the ceremony; the city lit up spontaneously, and the ritual stuck. It has grown into the Fête des Lumières: four evenings (always spanning December 8) when international artists project and install light works across the Presqu'île squares, the Fourvière basilica, the cathedral and the river banks, drawing crowds the city counts in the millions — commonly around two million visitors across the festival — and every Lyonnais still puts the candles in the window on the 8th itself. The installations run roughly from 7 or 8 p.m. to midnight (the detailed programme is published each autumn by the City of Lyon), the center closes to traffic, and the whole UNESCO-listed core — 500 hectares inscribed in 1998, from Fourvière hill across Vieux Lyon and the Presqu'île to the Croix-Rousse slopes — becomes a single open-air gallery.

December suits the rest of Lyon's character. This is bouchon weather: the city's taverns were built for cold evenings (quenelles in Nantua sauce, gratins, slow pork), the Halles Paul Bocuse market runs its festive season (oysters, Bresse poultry, foie gras), and the year's Beaujolais Nouveau — released the third Thursday of November just up the road — is still being argued over in the wine bars. Days are short but Lyon keeps its winter culture indoors: the Lumière Institute's cinema programme, the Musée des Beaux-Arts (France's largest provincial fine-arts museum, in the Palais Saint-Pierre), and the traboule circuits of Vieux Lyon, which are at their most atmospheric in lamplight.

The alternatives are respectable. Late September–October brings the Festival Lumière (the Lumière brothers' city celebrating cinema, founded 2009), the Beaujolais harvest and the first mâchon season warmth; May–June gives the Nuits de Fourvière concerts in the Roman theatres and terrace weather on the Rhône banks. Summer proper is hot and sleepier, as Lyon empties toward the Alps and the sea. But the December festival is Lyon's unique claim — the one week when the city performs itself — and for a first visit, that is the best experience by definition.

December 8, 7 p.m.: every window on your street flickering with its row of little candles, the basilica above the Saône mapped in moving gold, and two million people walking slowly, looking up.

The festival's true center is not a projection but a staircase: climb to Fourvière on the night of the 8th and look down — the candle windows make a second, private festival across every courtyard and hillside, tens of thousands of flames the official programme never lists. Lyonnais consider the lumignons the real event and the light art the frame. Stay for the 8th itself, not just the festival's opening night, or you will have seen the frame without the picture.

• Book a year-deep — Festival hotels inside the Presqu'île sell out months ahead; the moment the year's dates are confirmed, reserve
• Centre on foot — Stay inside the festival perimeter (Presqu'île or Vieux Lyon) and walk; streets close and the metro runs free and late on festival nights
• Days for the old town — Traboules, the cathedral and the museums by day, festival from dark; sleep in, Lyon runs late this week

The festival is weather-exposed and crowd-dense: December nights run 32–41°F (0–5°C), rain can soften a night's installations, and the Saturday of the festival is one of the most crowded urban nights in France — the city has cancelled editions before for security and weather (2015), which is worth remembering when booking non-refundable travel. Bouchons fill with festival diners; book dinners when you book the room. And the lumignon tradition means the 8th itself is sacred and quiet in pockets — plan the big installations for the other evenings.

Fix the festival dates when the City of Lyon publishes them, book a Presqu'île base and two bouchon dinners, and keep December 8 evening free for Fourvière.