Joint pain during cold weather can be caused by both the barometric pressure changing and lower blood flow due to the cold temperatures.
You can help relieve the increased joint pain from cold weather by dressing more warmly and wearing more layers of clothing to keep your joints more warm.
Taking some joint pain medication and also some aspirin or other pain medication can also help relieve joint pain during cold weather.
Doing some stretching exercises as well before going out into the cold weather can help loosen your stiff joints and help alleviate the pain from the cold weather.