I am planning to visit Taiwan in August 2013, how is the weather and which month is best to go

It would be hot and rainy in Aug. I read the past weather records which show that the average temperature then shall be around 28C, so summer clothes will be necessary. Besides, you may meet frequent rainy days, so raincoat is suggested to be prepared.

Well, personally, the best month to travel there should be Oct. to Nov.

I am going to Taiwan that day too. Hope the weather is good.