Self-rescue.
How many times do you need to see it before you believe it?
People don't take these threats seriously and then they get either seriously harmed or die. The good news is that technology and warning have both seriously improved in the last 100 years; those who are killed by a natural disaster are down huge, 90% or more, over the last 100 years.
Hurricanes, for example, were many times detected only on approach and thus by the time you knew there was serious trouble coming it was too late to do much in advance. There were a huge number of them that nobody knows about at all because other than a hapless ship that wandered too close nobody ever saw the "fish spinners." Today we have satellites and thus anything incipient is known when it starts; this is an enormously good thing.
But there are many disasters that give little or no warning. That it was going to rain a lot in the path of Helene was known; that a cold front was going to drop the sort of moisture it did in front of it into many of the mountain areas was not accurately forecast nor could it be. But -- that it was raining heavily in the two days previous was certainly something you could take note of. The "set up" for what happened is very similar to what occurred in 1916 -- and so was the outcome. Similarly we can tell when there's a risk of tornadoes in a given area today but not exactly where one will form or strike. Earthquakes are, with few exceptions, 100% no-warning events. You can determine you live in a seismic zone (e.g. New Madrid, San Andreas, etc.) but there is no way to know when the event will occur.
Many people believe that a "100 year flood" only happens every 100 years. False, but even if it was true how long ago was 1916? Uh, yeah. No, a "100 year flood" means that there is a one percent chance each year and each trial, that is, each year, is independent just as is a coin toss and thus that one year did or did not have a flood has no bearing on whether the next year will. To be more-accurate (I fat-fingered this originally, so this is corrected) you have a 99% chance per-year it won't flood. So if you live in a place that has a "100 year flood" risk over a 30 year mortgage there is a 73.97% chance you will not get flooded -- and a 26% chance you will. If you do get flooded in year 10 the risk of it happening again over the next 20 is about 18%.
That's right -- you have a one in four risk of getting hosed over 30 years of living somewhere under that threat and if you do get hit in year ten you have an approximately one in five-and-a-half risk of getting nailed again over the next 20 years if you stay!
By the way if you're in a place considered a five hundred year flood area the odds aren't much better; its 99.8% likely per year you will not flood but cumulatively, over 30 years you still have about a six percent risk of getting screwed. You probably think you are almost-certainly safe because 1 in 500 would put such events at least five human lives apart and thus "it ain't gonna happen." You're wrong.
These are mathematical facts.
Second, when and if it happens the help, whatever it, will go to the highest-density places first. It has to because all resources are finite and thus the correct move is always to help the most people fastest and first. This is the way triage is and its not cruel or anything of the sort; it is simply doing the best for the most you can with what you have available. But do not mistake the fact that those resources will go there means you want to be there; if there are one million people in an area you're one in a million and if only 100,000 can be helped you have a 1 in 10 chance of getting that assistance. 90% of the time you still go without and while the more-isolated place might not get any help for two weeks if you're in the 90% it doesn't matter, does it?
Concentrate your efforts on the basics of human need because in a disaster that's what matters most and expect even in a population area to be able to self-provide for at least a week. The first and most-basic human need is air; if you can't breathe it you're dead. Fires and toxins are real risks, but they're also ones that when it comes to breathable air your best option is to run at the first hint of trouble no matter where you are.
Second is drinkable water. Assuming you are not inordinately stressed you might make three days. You're probably worthless in two days and children are more susceptible to serious dehydration because their skin area is larger on a percentage basis, so they typically cannot make it past two days and are effectively useless in one day. Do not expect help to reach you under any circumstance until roughly that amount of time and perhaps more. Even with "local" relief that ignores exhortations to not go help personally (like here after Helene) it still will take that long because until people can get in there that's just how it is.
Any allegedly "fresh" water source after a disaster has to be presumed contaminated and unsafe unless you have the means to treat it, and there are chemical contamination risks that cannot be reasonably mitigated in a disaster situation at all with water at ground level. If you have a traditional hot water heater and your home or other residence is physically intact you have somewhere around 50 gallons of usable water in it. It should still be filtered with a Sawyer and/or treated with Aquamira drops (yes, buy both well in advance!) before consumption, particularly after a few days, but it will not be full of contaminants because it was full of clean water when the system went down. Keep a short hose around for this purpose and make sure you turn off the electrical or gas feed so once you start using it when water is restored it does not "dry fire." If you do not have any source of stored water (e.g. you have a tankless system and didn't fill anything in advance) then bottled water is your next and last resort. Everyone needs to be prepared to deal with this all the time; even if you're on a private well if there's no power the pump won't work (more on that in a minute.)
Third is personal shelter from elements, which includes clothing and similar. Enough to be out of the wind and elements (e.g. rain, etc.) is frequently enough but not always. Being wet, particularly in wind, can nail you with hypothermia even in moderately cool temperatures and in colder temperatures it is rapidly deadly. Some of this is beyond your control and if your housing is destroyed in adverse circumstances securing from that problem is, after immediate threats (e.g. incoming flash flooding) your first priority. Tools of some description, all the way down to a pocket knife, make a difference -- perhaps a really big difference. Having some preparation against this (e.g. a shell rain jacket, disposable space blankets, etc.) is inexpensive and everyone should have at least some elements of that available at any time.
The last utter essential is personal protection. It would be nice if people didn't try to take advantage but some will. Remember that the option to accept a "lesser injury" does not exist when there is no prompt medical care available, and there won't be in this situation. Exactly what you choose to do in this regard is a personal choice and I won't go into it on this side of the blog but it is critical to remember that any significant injury can trivially wind up being fatal if you can't get medical attention for a day or two.
The rest is very situational but these first points are not.
Expect communications by "ordinary means" to be unavailable. This time around Starlink worked when nothing else did -- if you had power available. No power? You're still screwed. And don't kid yourself as to the requirements either; those units require quite a bit of juice, about 100 watts which is non-trivial.
Note that in an actual emergency where ordinary communications (e.g. your cellphone) are unavailable any means of transmission, on any frequency, is legal to summon aid to prevent the imminent loss of either life or property. One of the cheapest means of doing this is any of the HAM-capable Beofeng radios -- the model 5RM is one of the better options, but hardly the only one, they are entirely portable and can charge over USB. They are not, however, waterproof -- there are major-manufacturer ones (e.g. ICOM) that are up to and including being submersible but they're a lot more expensive. Note that while listening is always legal without any sort of license at all it is illegal (and the FCC means it) to transmit on Ham bands without at least (for these) a Technicians license -- however in an actual emergency where serious and imminent threat to life or property exists and regular communications are unavailable it is lawful to use anything you can manage to talk to anyone on any frequency.
§ 97.403 Safety of life and protection of property.
No provision of these rules prevents the use by an amateur station of any means of radiocommunication at its disposal to provide essential communication needs in connection with the immediate safety of human life and immediate protection of property when normal communication systems are not available.
§ 97.405 Station in distress.
(a) No provision of these rules prevents the use by an amateur station in distress of any means at its disposal to attract attention, make known its condition and location, and obtain assistance.
(b) No provision of these rules prevents the use by a station, in the exceptional circumstances described in paragraph (a) of this section, of any means of radiocommunications at its disposal to assist a station in distress.
In advance look up the local repeaters in your area and program them in. Repeaters are typically located up high, have decent power and someone who is competent operating and maintaining them. You can listen lawfully any time you want; if you can hear a repeater you can probably get to it, and the Hams that operate them will put a lot of effort into getting those back on the air expeditiously because they are one of the key means of communications in emergencies. Also program in 146.520Mhz as a last-ditch; that is the universal North American (US and Canada) simplex (non-repeater) calling frequency and if there are Hams in the area with a radio on standby in an emergency if you're in range they will likely be able to hear and talk with you. The best strategy with one of these in an actual emergency, after one attempt to reach the local repeaters, is to check once an hour on the hour listening for others; remember that once the battery is depleted the radio is worthless without a charge and it takes a lot more power to transmit than receive. Don't waste the power you have in the unit if there is no charging source.
This is a literal $30 piece of equipment that can save your life; if you have an EPIRB/PLB that works in extreme emergencies as well but they're expensive and these are not plus once you set off an EPIRB/PLB it is "used" as the battery will be depleted and since it sends coordinates you have to stay put once you set it off or they go where you no longer are. Just be aware of the limitations of whatever backups you have but do have one or more.
Another thing to know: Starlink is working on direct to phone links. How far away that is for general use (they're testing with T-Mobile now) I do not know, but for low-bandwidth (e.g. text message) applications in the next few years this probably will be available and again is a life-saving thing if and when it enters operation. The hardware is not cheap for "regular" and "mini" "full" Starlink kits (~$600 or so) and the bad news with them is that at present they cannot self-provision, so in an emergency you can't turn it on if you have one stored at your location. Starlink may eventually fix this (and should, as it makes "terminal sitting in box" a VERY useful emergency communications device) but as of right now with no way to get to the Internet separately on a non-active unit you can't activate it.
Carbon-based fuels and all that run on them are your friend in such a circumstance. Generators, chainsaws, heavy equipment and similar all run on carbon fuels. Note that gasoline should be rotated at least once a year if stabilized and non-ethanol and yes, you do not want ethanol in the fuel if at all possible for this use. If you're even modestly away from civilization or could be cut off from power for any extended period of time two 5 gallon cans you rotate at least once a year (put them in your car and go get new fills) is an excellent emergency investment, assuming your residence survives. Those of us who have lived in Florida know darn well that those gas cans can be life-savers when a hurricane destroys the power feed to your area. That little generator will keep your refer and a few lights going. Consider the inverter models if you don't have one already and are only after real emergency use (e.g. the refer and a few lights, or your fuel-driven furnace controls and blower) -- they sip fuel compared to the older "straight" models under light loads; a refrigerator cycles on and off and modern LED lights consume almost nothing power-wise. Instead of close to a gallon an hour these will often run anywhere from three to eight hours on a gallon of fuel. Any generator needs to be exercised, with a load on it, every couple of months for 20 minutes or so because you must know it will start if you need it.
If you're on a well without prior planning your pump will not work on a backup generator; the starting current requirements are too high. You can put a soft starter in and if you have a 240V capable generator you should as with one a modest generator will run your well pump. Without a soft starter look at the label on the pump motor for "LRA" (locked-rotor amps) as that's what the generator has to be able to deliver without tripping on a "surge" basis or it will not start it. Microair makes a suitable unit (they have both 120V and 240V units available; there are other brands for RV use that will work for 120V pumps but most well pumps are 240V.)
In colder climates pay attention to your heat source(s) and a backup for whatever you use for heat is not a suggestion. Heat pumps are worthless without utility power; they simply draw too much power to run reasonably on a backup generator, except perhaps on a natural-gas fueled whole-house unit. A gas or propane furnace will run on a small generator if you have a transfer switch for it which is quite inexpensive and you should put one of those in for that specific reason even if you don't have a larger generator and transfer switch (which are expensive) setup.
Note that just now the media is full of stories about "full time" and "in major area" response on the ground. Its been over a week since the storm hit and had cleared off and just now we're seeing reports of government helicopters, larger aircraft and similar supplies for relief -- up until now it has all been private parties doing it because they want to help those in the area and government relief, with few exceptions, has been, like in so many other cases, absent.
In short expect that even in a heavily-populated area you are on your own for a week and had better be able to deal with that. In a less-populated (or rural) area it will likely be two weeks or more before you have anything approaching reasonable access to relief efforts, and thus you need to be prepared for two week to a month of being cut off. If you live somewhere that access can be seriously damaged (e.g. there is only a single mountainside secondary road that reaches your location) you need to be contemplating how you'll deal with that if the road is seriously compromised or destroyed and either have a plan to deal with it or be prepared to bug out if there's any possibility of it happening -- even if the odds are very low.
Take this seriously folks and realize that you cannot outrun either a mudslide/flash flood or storm surge. Surge is something you have some warning with as hurricanes are well-forecast but flash floods are in many cases akin to tornadoes and while the conditions that can lead to them are usually forecast the event itself often occurs with very little warning. Both move at speeds that are wildly faster (double or more!) than you can run and in any vehicle if you encounter even one obstruction trying to flee it will overtake and kill you. The only sane option is to not be there, but if you're trapped where there's no good way out then you have to be able to deal with whatever happened until you can either cut your way out or relief can get to you and in the first days to a week or so the most-likely people to be able to and who will help you are private individuals who live in the area -- not the government in any form whether federal, state or local.
Now after you've read all this above and let it soak in for a bit go into your bathroom or kitchen and do an assessment of your medicine cabinet.
What happens if everything in that cabinet is gone and you can't get more? If you can do something about that and don't all the above may well mean exactly nothing.
Next take off all your clothes and find a mirror in your house. Have a good look and don't lie to yourself.
If you have to hike 5 miles over rough terrain to get water and haul enough back for a couple of days for the people in your household can you do it? Incidentally that requirement is roughly a gallon per person, per day and each gallon masses 8lbs so you're talking about "rucking" 35-40lbs (with the pack) on the five-mile return if there are four people in your household. If you have to do it, and can't, you will die. Or if you need to do the same thing with 3-4 gallons of gas for a generator (you do have one, right?) to run your well pump for a few days and keep the refer operating -- can you?