Here is a quick Cameron Highlands weather forecast for the next five days. Generally the weather in Cameron Highlands is cool with a daily average temperature of 25°C and nightly average of 12°C. However the weather is also affected by the overall weather in Malaysia. So if the weather in the lowlands is hotter than usual, Cameron Highlands will not be as cold as it supposed to be. And during the rainy period in Malaysia such as monsoon or heavy convection rain, Cameron Highlands can get pretty cold.
So do bring enough warm clothing for those cold nights and rainy periods. Generally you can wear shorts if the temperature is just mildly cool. Like the rest of Malaysia, the weather in Cameron Highlands is unpredictable, so do bring along an umbrella or raincoat.
There are many short easy to carry umbrellas as well as disposable raincoats that you can purchase from convenience store and pharmacy.