For most of the year, Phoenix has very pleasant weather that makes it perfect for outdoor activities. When the summer months hit, the temperatures can increase dramatically. Camelback is located in the northeastern part of Phoenix, which is in a dry desert.
Staring around the end of May, when the temperatures start to rise you need to be extra cautious. There is little shade on the trail, expect for during the morning when some parts will see it. Anything over 80°F and you should plan to have extra water, extra time to hike, and proper cloths to keep you cooled off.
Look at the temperature and if it is over a 100°F, then it is best to not do the hike. The hot rocks mixed with a strenuous climb is a recipe for heatstroke. This is were it can get dangerous for people who do not take enough water or hike when it is too hot.
Another time to be careful is during the monsoon season, during the later summer months. We have haboos (dust storms) that can easily roll in on a short noticed. Along with this, we can have heavy rain, microburst with hail, and wind during a monsoon storm.
Pretty wicked to see, but not when you are trying to climb up rocks. If you are around when it rains, take a look by the Praying Monk area on the north west side of the mountain. You will see small waterfalls coming off of the mountain.