Tornado, flood, hurricane... no one knows what other unthinkable events may occur.  For about $100.00 you can build a robust, easily portable 3-day survival kit for two people.  All products are copyright their respective owners.

• Small, off the shelf survival kit.  For example, The Super Ark by Survivor Industries, Inc.  It contains food and water for one person for up to three days; first aid kit with moist towelettes, band aids, gauze, alcohol wipes, aspirin and anti-bacterial ointment; blanket, candle, hand warmer, light stick and waterproof matches.  Be sure to include one for each member of the household!
  
  
• AM/FM, battery operated radio.  Do not keep batteries in the radio (to avoid corrosion), keep them in a resealable plastic bag with extra batteries.
  
  
• Extra prescription and over-the-counter medication for anyone in the household that needs it.
  
  
• Multifunction tool that includes at least a knife, pliers and screwdrivers.
  
  
• Battery-powered flashlight, preferably LED bulbs as they last longer.  Do not keep batteries in the flashlight, keep them in a resealable plastic bag with extra batteries.
  
  
• Large container of wet wipes.
  
  
• Poncho.  One for each member of the household.  Preferably include at least one red/orange and one camouflage.  The red/orange can be used where high-visibility is desired and the camouflage where concealment is desired.
  
  
• Plastic bags that zip closed.  Can be used to store belongings and keep them free from moisture.
  
  
• Dust masks/respirators. The least necessary item but, considering the low cost, it's good to have for protection against dust.
  
  
• A five-gallon bucket is the perfect container for all of the items above for two people.  It is relatively water-resistant and easy to carry.  An orange one provides great visibilty.  Can be used as a seat, step-stool or latrine.
  
  
• Anything else vital to your particular situation!