Khamis Mushait and the Asir highlands are at their most pleasant from October to April, when days are clear and cool at altitude. October and November bring crisp weather after the summer monsoon, with good visibility and green hillsides. December to February can be cold at night — temperatures occasionally drop below 5°C — but days are sunny and mild.
The summer months from June to September are unusual for Saudi Arabia: the Indian Ocean monsoon brings cloud, drizzle, and genuinely cool temperatures to the highlands. Average highs in July and August stay around 20–22°C, making the Asir a popular domestic summer destination for Saudis escaping the Gulf heat. Roads can flood and visibility drops in heavy cloud, but the landscape is lush and dramatically misty.
Avoid visiting during major Saudi public holidays if you are relying on tourism infrastructure — hotels fill and sites become crowded. Ramadan brings reduced hours for many services.