Am I liable for damages caused by an act of nature?

If a truly is an act of nature, you probably are not liable. However, if there are things you could have or should have done to secure the canopy, then you could be held liable. Your insurance company for your homeowner's policy can make a determination.

In my opinion, you are not liable for an act of God.s

Possibly, if you failed to have it secured. While winds are acts of nature, they are not unsuspected or unanticipated acts of nature, and if you did not have your canopy secured properly, you may be liable. I would go ahead and call your homeowners insurance company and give them all the information. A failure to timely notify your insurance company of the fact a claim is being presented against you might possibly adversely affect your coverage.

All negligence involves an "act of god" at some point in the causal chain, otherwise it wouldn't be negligence, but rather an intentional tort, like battery or trespass. Their case against you is weak, but is it worth destroying your relationship with your neighbors by fighting? Offer them an apology and some nominal compensation.

This is a tough question. You should contact your homeowners insurance (depending on the amount of the repairs to your neighbors property as to whether it is worth making a claim, taking into account your deductible and whether the claim will raise your rates in the future. I found the following case law: The court then advised the jury that an act of God meant such an unusual and extraordinary manifestation of the forces of nature that it could not normally be anticipated or expected; that a defendant was not liable for a loss occasioned by an act of God unless his own negligence had contributed to the damage; and that in order for a defendant to sustain the defense of act of God, he was required to prove by a preponderance of the evidence that the icy condition was of such an unprecedented nature that no ordinary or reasonable amount of care would have prevented the damage. It has been held that in order to constitute an act of God, a storm must be so unusual in its proportions that it could not be anticipated by a defendant. (Inyo Chemical Co. v. City of Los Angeles (1936) 5 Cal.2d 525, 532-535, 55 P.2d 850.) Also, a rainstorm of merely unusual intensity is not an act of God. (Sturges v. Charles L. Harney, Inc. (1958) 165 Cal.App.2d 306, 320, 331 P.2d 1072.) Likewise, a wind which is not a hurricane nor of such unheard of violence as to be beyond all contemplation or expectation does not amount to an act of God. (Holt Manufacturing Co. v. Thornton (1902) 136 Cal. 232, 235, 68 P. 708.) In the instant case, ice was not in the least unusual in the Larkspur area in the winter, and its formation on the surface of the Bon Air Bridge was an occurrence which clearly cannot be deemed beyond all contemplation or expectation. I was not able to find a case that discussed your exact scenario. The foregoing case was a personal injury auto collision, not a property damage case, but other cases state the same general theory that an Act of God defense may exculpate you from liability so long as there is no human intervention giving rise to the damage or injury. There are a bunch of cases where branches or entire trees blew onto a neighbors property and they were held NOT to be an act of God. If I were the neighbor I would argue that you knew at this time of year winds can be very high and that your canopy should have been retracted or taken down during the winter months. You, on the other hand, can raise the act of God defense because it presumably never happened before and you had no idea this could even happen. You may also have a claim against the manufacturer of the canopy or the contractor that installed it. But since we are talking about property damage and not an injury to a person, either your insurance or their insurance should cover this incident.

I understand that the wind caused your canopy to blow onto your neighbor's roof and that wind is a force of nature. However, I think that a broader view of the situation is appropriate. The canopy was yours and there is an argument that it was not properly secured. Additionally, if the damage is minor, good relations with a neighbor are important. So although the decision is yours, I think prudence (and Dear Abby) would recommend payment.

No. This is called an Act of God in law. This assumes you did not do anything negligent about the matter, like failure to maintain etc etc.