Season is June to August if you want to use a shorty/trunks. With wetsuit you can go all year around. The water doesn't freeze, but it will get really cold in the winter: -10°C. More reasonable would be mid April to mid November. If your using a thick wetsuit, boots, gloves etc.
In summer generally very light winds, autumn would be considered the windy season here with quite strong winds. We have no consistent winds here, so there are no really dominant wind patterns. Best is however NE, E, SE.