When travelling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Derry is roughly less than Belfast International. You can assume this to be the case over the next 1 days.
Our data indicates that the weather will be 19 °C on average in the month of July. The temperature in Belfast International is typically hotter than in Derry. If you're traveling when the temperature is at its warmest, push to plan early, as flight price and availability will have an impact on your travels. For the best results, search for flights well in advance or after peak season.