Poor Circulation: This is the most likely diagnosis due to the common complaint of cold feet without other symptoms such as itching or redness. Poor circulation can be due to various factors including environmental conditions, smoking, or underlying vascular diseases.

Hypothyroidism: This condition can cause feelings of cold intolerance, leading to cold feet. It's a common endocrine disorder that can present with nonspecific symptoms.
Anemia: A decrease in red blood cells or hemoglobin can lead to reduced oxygen delivery to tissues, causing feelings of coldness in the extremities.
Diabetes: Although typically associated with neuropathy and other symptoms, diabetes can also cause poor circulation, leading to cold feet.

Deep Vein Thrombosis (DVT): Although less likely, DVT is a potentially life-threatening condition that can cause coldness in one leg. It's crucial to consider this diagnosis to prevent missing a condition that could lead to pulmonary embolism.
Peripheral Artery Disease (PAD): This condition involves narrowing of the arteries, which can severely limit blood flow to the legs, causing cold feet. It's a significant risk factor for cardiovascular events.

Raynaud's Phenomenon: A condition that affects blood flow to the fingers and toes, and sometimes the ears, nose, and lips. It's characterized by a sudden and temporary narrowing of the arteries in response to cold temperatures or stress, but it can also present with cold feet.
Buerger's Disease: A rare disease of the arteries and veins in the arms and legs, which can cause coldness, pain, and other symptoms due to reduced blood flow. It's strongly associated with smoking.