When travelling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Birmingham is roughly greater than that of Yellowknife. You can assume this to be the case over the next 11 days.
We forecast the temperature to be around the 22 °Cs in July, on average. The temperature in Yellowknife is generally the same as in Birmingham. Book flights in a timely manner in correlation to your departure date.