First of all whenever there is low rainfall and higher heat then there are problems.You shall notice that there are brown colored needles which dry up and then drop of. Sometimes they start at the tip and then move towards the branch. This shows drought and you need to soak in lots of water to overcome. However if you notice the brown needles going from the middle to the tip then these are due to natural process. Another problem is the presence of spider mite. Take a white sheet of paper and place it under branch. Now bang it with your palm. If any kinds of specs gather on the paper by rubbing your palm on the paper then there are insects. If it smears into any kind of visible signs then there may be spider mite. Spider mites are tiny insect and they suck the juice out of the plane. To remove them you just have to spray the plant with water. You also need to check the main trunk and the roots system to ensure they are not left dry in hot weather. To check this you can take a rod and insert it at a few feet away from the trunk and check whether the soil has adequate moisture. For most trees it is good to have eighteen to twenty four inches of the soil moist. You can use a sprinkler to water around eight inches of water. You can put coffee cup below the sprinkler. When the cup collects two inches of water that means the tree has been sprinkled with required water. Another problem is that of the root system when the tree is a seedling and due to spiral and improper root growth it doesn't grows properly and causes problems when old. Now check the base trunk of the tree because if there is a natural flair of growth then it means that the root system is fairly developed. That's it.