It will be cloudy in Hk on April 14th, with a temperature of 20-27C. No weather forecast for Guangzhou and Shenzhen now, since the weather forecast is only for 7 days only. However, Guangzhou and Shenzhen are near to Hk, so the weather may not very too much. I think you can just take a thin and light overcoat in case of any bad weather. Meanwhile, pay attention to the weather forecast later, since the nearer it is, the more correct the weather forecast is.