As a long time Florida resident and a boater, I can help with answering this one but just for offshore Florida and the Bahamas. The summer season, beginning in mid June and going through September, has primarily low winds and because of that, low waves. Any winds in the summer are from the east and with the Bahama chain 60 miles from Florida, helps to keep the wave height down. The other months have a different weather pattern where the wind are higher and sometimes come out of the north (cold fronts). When the winds are from the north, it kicks up the Gulf Stream because the GS is moving south to north and the northern winds pushing against the gulf stream makes waves. The higher the wind, the higher the waves. Cold fronts can create waves as high as 15 - 20 feet. It's weird because near shore the water is flat but 5 miles offshore its crazy rough. The problem is that the summer is also hurricane season which everybody knows can put a real damper on your cruise. Weather is obviously important to boaters so I set up a weather station at my house and it posts in real time to Weather Underground's web site. My friends who are boaters can see the current conditions and along with some marine weather prediction web sites and live webcams on the ocean, we have a pretty good handle on if we should go boating and how far we can go out. This info is only for the Florida waters and around the Bahamas. I don't know anything about other locations