When traveling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Da Nang is roughly greater than that of Cancun. You can assume this to be the case over the next 12 days.
Expect the weather to be around 35 °C on average in June. 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 Cancun is generally colder than in Da Nang.