Why do my feet and ankles swell up? A common issue for a lot of people during the hotter summer months, is swelling tin the feet, ankles and calves. Peripheral Oedema (or Heat Oedema), is a result of the heat causing blood vessels to dilate (expand) which then causes body fluids to move to your extremities; legs, feet and hands, via gravity. Excessive walking, sitting, and standing in one spot for a prolonged period of time without moving allows gravity to further pull fluids