October to April is the only realistic window for visiting Biskra. Summers are among the hottest in Algeria — temperatures regularly exceed 45 degrees Celsius and occasionally approach 50. The city essentially shuts down in July and August. Spring (March to May) is ideal: warm days, flowering desert plants, and the date palms in full leaf. The date harvest runs from October through November, when the markets fill with fresh Deglet Nour dates and the atmosphere in the oasis settlements is at its most lively.
Winters (December to February) are mild and pleasant but can bring cold nights. Rain is infrequent but possible. Ramadan, which falls at different times each year on the Gregorian calendar, is worth checking before you go: most restaurants close during the day, though the evening iftaar brings the city alive in a way worth witnessing.