From sunshine and bikini-weather in December to mayday-grey-day in August: everything is possible in Ericeira and conditions can change in an instant! There are although some general guidelines for when to visit depending on your holiday plan:
September and October are most predictable and usually always amazing in terms of weather and waves.
June, July and August are always warm, it might get pretty windy and foggy at times!
March, April and May bring mild weather, waves are good for everybody and from sunshine to rainy days, everything is possible.
This is true for November, December, January and February too, just that temperatures cool down a bit more, specially at night. Waves are usually gnarly during the winter months!