One of the reasons why i like touring by bicycle, is because you get to experience the environment - when there's a mountain, you get tired getting up it; when it rains, you get wet. You're a participant, inside the landscape - not a spectator.
Here's a few websites with what weather to expect when (with expected dates wehn I'll be there)
http://www.theweathernetwork.com/weather/npxx0004 (everest base camp; 10-12/6)
The higher above sea level, the colder it gets - the normal 'environmental lapse rate' (how much it gets colder as you go higher) is about 6.5°C for every 1000m climb. So if it's a pleasant 25°C on the beach in Capetown, then you can expect temperatures on Table Mountain 500m higher to be just over 21 °C (without any wind chill taken into account). At 5200 m above sea level (the altitude at the base camp) it would be well below 0°C.
Enough Geography - I have to go Box the Bike. 3 Cheers to Wolfgang from Linden Cycles who removed the peddles today with his oversized peddle-tool after i struggled for more than an hour to get them loose last night.