The Auschwitz-Birkenau museum is open year-round, with longer opening hours in summer (May to September, when it opens at 7:30am and closes at 7pm or later). In winter, the site closes earlier and some outdoor areas can be bleak in cold weather — though the emptiness of the site in winter has its own particular weight. Crowds are heaviest in July and August, when tour groups from across Europe and beyond converge and timed entry slots fill weeks in advance.
The best times to visit are spring (April–May) or autumn (September–October), when the weather is reasonable and crowds are manageable. January 27 — International Holocaust Remembrance Day — sees a particularly significant commemoration ceremony at the site, with survivors (increasingly elderly now), dignitaries, and large public attendance.
Book your timed entry slot well in advance if visiting between April and October. Mid-week visits are quieter than weekends. Arrive at opening time if possible, before tour buses arrive.