Spring (March to May) and autumn (September to November) are the best times to visit Jerash. The weather is warm but not hot, the light is good for photography in the morning and late afternoon, and the site is less crowded than in the peak summer months. Temperatures in spring and autumn range from 15–25°C.
Summer (June to August) is hot — temperatures regularly exceed 35°C in the open ruins — and the site can be very crowded by late morning. If you must visit in summer, arrive as soon as the site opens (typically 8am) and plan to finish by noon. The Jerash Festival of Culture and Arts takes place in July and August and brings concerts and performances to the ancient theatres, which is worth timing a visit around if you can tolerate the heat.
Winter (December to February) is cool and quiet, with occasional rain. The ruins are atmospheric in overcast light and you may have large sections of the site to yourself.