Hi after September you are presented with the problem of the "marés vivas equinociais"

In October each year occur these "marés vivas equinociais" – the sea becomes very unpredicatable, the swell increases in both intensity and unpredictability

The seas can be very dangerous off the west coast of Portugal and north western Spain at any time of the year – but are particulary so at this time of year

http://www.meteogalicia.es/galego/informacion/prediccion/maritima/marea/iforzas.htm

http://www.marinha.pt/Marinha/PT/Menu/NoticiasAgenda/Noticias/mares+vivas.htm

Best wishes

Ant