The locals in the area told me that september was a good time to go. they said that the wind is kind of sketchy during July and august and there there wasn't a whole lot and not a sure thing.
Surely Spring is better, but the locals (the locals who work for Real Kite on theisland of Cape Hatteras and have a shop and one of the biggest kiteschools) advised me to come in September. Said it was a good time... I have been to places during the "best times" only to find myself doing all the local sites because there was no wind.
When you depend on certain weather conditions for a sport whether it be waves or wind - it is always a hit or miss situation. There are things to look at (moon cycles and other), but nothing is a sure thing.
The last really big kitesurfing events organised in France over the last year and the locations which are "99%" sure to have wind.. well go figure.. most of them only had wind on 2 of the 7 days of the organised event.. and these are locations where the wind blows "non stop".
When you follow and are looking for the wind it is a hit or miss.
Even when the weather report has announced wind.. sometimes it doesn't show up.. and sometimes when they announce nothing.. well the wind shows up in time and honor. The weather reporting is not a perfect science and is very unpredictable. I guess it is part of the game. But there are plenty of other things to do over there on the Island (hopefully we wont' be doing many of them), but there is enough to do to keep one busy.
So, I am not too worried.