Hot weather and small bumps on the hands is a kind of eczema. Eczema is usually more obvious in summer, when hot weather causes the sweat glands of the skin to excrete a lot of sweat, and if the sweat is not excreted properly, it will stimulate the subcutaneous tissue on the surface of the skin, which will easily lead to itchy skin, and at the same time stimulate the epidermis around the hair follicles or sebaceous glands, forming an inflammatory reaction, which is seen by the naked eye as one small bump. Therefore, when the weather is hot in summer, it is easy to have small bumps on the hands.