Your tree could be turning brown and dropping needles as part of it's normal
needle shedding process. This would typically occur in the fall, extreme environmental conditions can increase this natural event.
If your tree has been browning all summer it could be a fungal disease.
Inspect the tree for Galls or any abnormalities in the stems or needles.
An Arborist can help you make a correct identification if you are unable to determine if this is natural or disease.
Your local County Extension Office can help you find a qualified tree expert in your area.