Normal swelling doesn’t cause any changes in the temperature of your feet. But if you’ve got swelling in your feet and heat in the foot or calf, it’s a cause for concern, because specific disorders lead to narrower-than-normal openings or blockages in the arteries and veins. For example, chronic venous insufficiency is a disorder where the leg veins don’t allow blood to flow correctly, leading to pooling in your legs (via Johns Hopkins Medicine). People who suffer from this have elevated temperatures in their skin, per an article in the Journal of Vascular Nursing.
Additionally, when the blood clots abnormally in the leg due to an underlying disorder, pregnancy, injury, or environmental factors, it can lead to deep vein thrombosis. According to the Mayo Clinic, the blood clot forms deep within the artery of the thigh or calf, causing a change of color, swelling of the leg and foot, soreness, and heat in the skin. Deep vein thrombosis can be dangerous because the clot can break off and travel to other body areas.
Diagnostic testing is needed to determine if your inflammation and warmth are from sinister causes. Treatment might include compression garments and devices, exercise, therapy, and medication.