In a case like this, you can take the defence of Act of God. When any natural calamity like earth quake, flood, cyclone etc affects a person without any human intervention and such act could not have been prevented by a reasonable foresight or care, then it comes under the clause of act of God. Therefore as the tree fell on your neighbour's house as a result of cyclone and high speed of the winds and it was not in your hands to control the speed from blowing the tree, this will fall under Act of God. This wind caused damage will be covered by the homeowners insurance. In such a case, the neighbour must not sue you, but even if they did you can take the defence of Act of God. Therefore you will not be liable to pay the price for their damage. It will be covered by your neighbour only.