With the popularity of these two sports growing rapidly Greece and in particular the Aegean Sea was discovered about a decade ago for its strong consistent winds through the Summer months.
Unfortunately the Ionian sea does not have the consistency of the Aegean which can blow relentlessly for two to three weeks non stop, winds never dropping below a force 4, but does have a consistent wind pattern of 7-10 days of calm followed by 2-4 days of excellent winds. The trouble is if you are on holiday for a week or ten days you might get a very dark sun tan and not much more, so it is difficult to recommend Corfu as a pure windsurfing destination, it also lacks hard core conditions that advanced surfer seek.
But it is a good place to learn or improve your skills if already on holiday, in some respects better than surfing hot spots as its never too crowded. Try raising a kite on a beach with another 50 or more kiters and you soon start to appreciate less than perfect places like corfu.
But of all the above are relevant from May to August, come Semptember its a very different story. The first southerly winds arrive mid September and hold strong until december. This tranquil easy surfing scene is transformed into an arena for advanced sailors only, with winds consistently exceeding force 7 and often reaching 9 with waves swelling to 4meters plus. These winds come approximately once every two weeks and last for 1-3 days accompanied with heavy rain. You need to get out on the water early and be well prepared for the day, more on autumn-winter surfing to follow.