Pingyao is best visited in spring (April-May) or autumn (September-October), when temperatures are mild, skies are typically clear, and the tourist crowds are manageable. The Golden Week holiday (October 1-7) is the most crowded period in the year — accommodation books out months in advance and the streets can be uncomfortably packed.
Summer (July-August) is hot (30-38°C) and busy, particularly with domestic tourists. Winter (December-February) is cold (-10 to 5°C) and quiet, with few foreign visitors and dramatically lower prices. The kang heated beds in the courtyard guesthouses are genuinely appealing in winter, and the old city is atmospheric when dusted with snow.
The Lantern Festival (fifteenth day of the first lunar month, usually February) sees the old city decorated with red lanterns — one of the better times to visit if you're in China during the Spring Festival period.