October to April is the only sensible time. Daytime temperatures in those months sit between 22 and 30°C, evenings can be cool enough for a light jacket, and Jebel Akhdar is even cooler — bring something warm if you head up.
May to September is brutal. Daily highs of 40–48°C, no shade in the souq during the middle of the day, and the fort tower becomes uncomfortable to climb after 9am. If you must travel then, be out at dawn and indoors by 11.
The Friday morning livestock market runs year-round. The Jebel Akhdar rose festival is the highlight of the calendar: late March into mid-April, when the damask roses bloom on the terraces and rosewater is distilled in the old villages. Eid al-Fitr and Eid al-Adha bring a busy holiday atmosphere — and crowded hotels — to the town.