When traveling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Hanoi is roughly greater than that of Tucson. You can assume this to be the case over the next 18 days.
Expect the weather to be around 39 °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 Tucson is generally hotter than in Hanoi.