When travelling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in St John's is roughly greater than that of Denver. You can assume this to be the case over the next 19 days.
Our data indicates that the weather will be 32 °C on average in the month of July. The temperature in Denver is typically hotter than in St John's. 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.