Samarra has a hot desert climate. Summers are fierce — temperatures regularly exceed 45°C from June through August, and the monuments at the Great Mosque sit fully exposed with no shade. Spring (March to May) and autumn (October to November) are the most comfortable times to visit, with daytime temperatures in the range of 20–30°C and cool evenings.
The Al-Askari Shrine sees its largest crowds during Shia religious occasions, particularly the anniversary of the martyrdom of Imam Hussein (Ashura, which falls in the Islamic month of Muharram) and the anniversaries of the deaths of the 10th and 11th Imams commemorated at the shrine. If you plan to visit the shrine during these periods, expect very large crowds and heightened security.
Winter visits are possible and the temperatures are pleasant, but occasional cold fronts from the north can bring rain and wind.