Drink plenty of it. Also, make use of sprinklers, water hoses, etc., to cool your body. Layers also keep in body heat. Legs do not need as much protection. Tights, long-johns or warmup pants are fine.
Most runners wear socks in the winter.
In very cold weather, wear a hat. Warm up slowly so as not to hurt yourself. After your run, be sure to stretch to prevent stiffness from developing. After you cool down, take a warm shower to help loosen up your muscles. Replacement of fluids is almost as important as in summer running.