September-March is the peak season for good weather and (not surprisingly) for tourism. High temperatures range from 65 F/19 C in September to 80 F/27 C in February. There is little rain during this period, but strong southeasterly winds occur in January and February. Summer is also when daylight hours are at their longest. In Cape Town, this means lingering drinks or dinner while watching a sunset, and some of the attractions are open later—such as the Table Mountain Aerial Cableway, which is open until 9 pm.
In the cooler winter months, the daily highs are usually in the low to mid-60s F/17-19 C. High rainfall occurs in winter, especially July and August, when icy northwesterly winds take heavy showers to the Cape Peninsula. Light snowfall can also occur in the mountains during this period. If you're not crazy about beach culture and crowds, the autumn and winter months are good for visiting Cape Town. By Northern Hemisphere standards, the conditions are mild, and rainfall is often followed by warm, sunny days. Expect abrupt weather changes year-round. Fog is one cause: It spills down onto the city from the mountains, leading to sudden temperature drops.
If you're going to walk on Table Mountain or negotiate other hiking trails, always check the weather before you leave. Also take a light backpack with additional clothing (a waterproof, windproof jacket is essential). The weather on top of the mountain is notoriously fickle. When surprised by poor weather, the most important thing to do is take shelter from the wind. Take particular care when standing on exposed, elevated view spots during strong winds. For weather reports, visit http://www.weathersa.co.za.