Oudtshoorn sits in a rain shadow between two mountain ranges and is semi-arid — hot and dry in summer (November to March), with temperatures regularly exceeding 40°C, and mild in winter (June to August), when it rarely drops below freezing but the evenings are cool. The Cango Caves maintain a constant temperature of 18°C year-round regardless of conditions outside.
The best time to visit is spring (September to November) or autumn (March to May), when daytime temperatures are comfortable for walking and driving. Summer is manageable if you start early and rest during the midday heat. Winter is the quietest season and perfectly pleasant if you don't mind cool evenings — the Swartberg Pass can occasionally close for snow in June and July, but this is rare.
The Klein Karoo National Arts Festival (KKNK), held in Oudtshoorn every year in late March or early April, is one of South Africa's largest Afrikaans arts and culture festivals. It draws large crowds and fills accommodation, so book ahead if your visit coincides.