The spatial pattern of monthly and seasonal rainfall fluctuations over the British Isles between 1942–1970and 1961–1990 are interpreted in the context of changes in atmospheric circulation. Increases in rainfall in autumn, winter and early spring occur largely in north‐ western ereas, whereas increases between April and July occur generally in eastern disricts. This is a consequence of an enhanced seasonal cycle in the vigour of mid‐latitude westerly circulation. An increased proportion of annual rainfall in the winter halfyear and an associated decrease in the contribution of summer (June, July and August) rainfall are consistent with changes in the seasonal distribution of rainfall and associated forcing factors suggested by coupled ocean–atmosphere models of future climatic changes.

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The regional climatic gradient between the north‐west and south‐east of the United Kingdom is analysed in the context of the fluctuating vigour of the mid‐latitude westerlies. The study period comprises the mid‐twentieth century period of atmospheric blocking and the more active westerlies that have characterized much of the 1980s and 1990s, especially in Winter. This change has coincided with increased regional gradients of rainfall, temperature and sunshine between north‐western and south‐eastern Britain. This is consistent with an enhanced climatic gradient across Europe and it is suggested that this may have been accentuated across the United Kingdom by orographic influences. These results also show some congruence with scenarios of climate change for the twenty‐first century, indicative of the sensitivity of the North Atlantic Oscillation (and mid‐latitude westerlies) to temperature change. This could contribute to a significant hydrological and environmental perturbation when viewed in the context of increasing demand for water in southern and eastern England.