It won't take much of a threat of a storm to make them send the boats and oil buoys to safety. And they would have to shut down the drilling of the relief well and move that rig to safety.
I was thinking about this last night.... once they stop the flow of oil at the surface, it will be difficult to tell if the blowout is continuing downhole. That is, the stong flow from the zone that is flowing, may travel uphole a ways and then enter a zone higher up the wellbore. They were losing mud at something near 13000' and had to sidetrack the well, so there is a lower pressure zone there most likely. And, any permeable zone between where casing was last set and the end of the hole could be pressuring up at this point. In fact, any zone near the end of any string of casing could be pressured up, if the wellhead is damaged as some suspect.
Keep your fingers crossed for the safety of the men drilling the at relief well. It is very dangerous business if there are unexpected high pressure zones along the way.