Coastal flooding in the Gulf of Lion is associated with storm-surges linked with south-easterly winds that push up the water toward the coasts. At a synoptic scale, these meteorological conditions are associated with a deep barometric depression near the Bay of Biscay. This is favoured by the negative phase of the North-Atlantic Oscillation that leads to a southward shift of the main storm track over the northern Atlantic. In the second half of the 20th century, the frequency of south easterlies shows a significant increase in the whole Gulf of Lion, paradoxically with the positive deviation of the North-Atlantic Oscillation. Changes in the mean atmospheric conditions at this broad spatial-scale have increased the probability of barometric depression near the Bay of Biscay and of south easterlies in the Gulf of Lion during the negative phase of the North-Atlantic Oscillation.