If you can’t do the long term stuff others have been mentioning here is a bit more short term stuff:

• Make sure you have bottled water. Ideally a few weeks worth per person in your household. Remember that cooking uses water too.
• Medication for as long a period as you can reasonably cover for the people in your household
• potassium iodine tablets to protect the thyroid in case of nuclear fallout
• Canned food
• remember your pets need stuff too if you have them
• in case there is an infant involved baby formula, diapers and other baby needs

More long term:

• look into MeshCore or meshtastic for communication
• radio with a hand crank + spare batteries
• medkit with bandages, tourniquet, etc. Also learn how to use it.
• we have 3 ways of heating our house: fireplace, electric and gas. I’m sure that won’t be possible for everyone but the point is diversification where possible.