In extreme conditions the soil from around the walls could expose the fibrous roots of the plants that are growing around the edges of the bed and make them vulnerable to frost, heat or drought. Depending on the plants that are grown in raised beds it may be necessary to add more humus to the soil to help it retain moisture. Once plants are mature, let the top couple of cm of soil to dry out before watering the plants then dig down about 15 cm deep from time to time to see how well the soil is retaining moisture and water accordingly.
Regular watering and some extra care over the drought periods will keep your plant in shape and spare you of serious problems caused by the lack of water. You can use irrigation to supplement natural rainfall during dry periods. The raised bed system also helps to reduce diseases, by directing water to the soil instead of wetting the leaves as the overhead irrigation does. Soaker hoses or drip irrigation are ideal as they may be placed directly on the bed. Even overhead sprinklers can also be used, they are not recommended because they wet the foliage are more likely to spread diseases.