When travelling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Abu Dhabi is roughly less than Changsha. You can assume this to be the case over the next 3 days.
Expect the weather to be around 43 °C on average in August. As the temperature peaks, try to get your plans done early, as flight price and availability will have an impact on your travels. The climate in Changsha is generally colder than in Abu Dhabi.