Even in summer it can get too cold for your horse to stand in the meadow or in the stable without a rug. You can then use a summer rug to protect your horse from the cold if winter rugs are too warm. A summer rug is usually made of cotton. This material is lightweight and breathable so that your horse does not get too hot. The rug is usually lined with nylon on the inside of the chest to prevent rubbing. The summer rug is also used for transport in the summer or to ensure that your horse stays clean after a good brushing or washing before a competition.
Summer rugs are not waterproof, so if it rains and you want to put your horse outside, you should provide him with a rain rug. Take a look for this in the category BR rain rugs.