San Fermín (July 6–14)
This is Pamplona's defining week. If you want to run with the bulls, attend the fireworks, or simply be part of one of the great European festivals, come now. Book accommodation six months in advance at a minimum — a year ahead is not unreasonable for anything central. Prices multiply, the city is packed, and sleep is largely optional for the duration.
The festival begins at noon on July 6 with the chupinazo — a rocket fired from the town hall balcony into a crowd of thousands in red and white. From that moment until July 14, the city barely stops. The encierro (the running of the bulls) happens every morning at 8am. Fireworks happen every night. The mood is ecstatic and very, very loud.
Spring and Autumn
April, May, and October are the best times for a quiet visit. The weather is pleasant — mild and often sunny — the old town is walkable without the summer crowds, and the prices are normal. The city's museums and restaurants are easily accessible.
The Camino
If you are walking the Camino Francés, Pamplona is typically reached on the second or third day out of Saint-Jean-Pied-de-Port, depending on your pace. The pilgrim hostels operate from March to October. Spring (April–June) and early autumn (September–October) see the most pilgrims.
Climate
Pamplona sits at 450 metres on the Meseta, and the climate shows it. Winters can be cold with frost and occasional snow. Summers are warm but not brutal — highs around 28–30°C in July. Rain falls year-round, with spring the wettest season. The Pyrenees are visible to the north on clear days.