Natural Hazards

There are many types of severe weather events that affect Delaware, such as hurricanes, severe thunderstorms, tornadoes, and winter storms.

Flooding Hurricanes Winter Storms Tornadoes


Flooding is the nation’s most common natural disaster. All floods are different. Some can develop slowly during an extended period of rain, or in a warming trend following a heavy snow. Others, such as flash floods, can occur quickly, even without any visible signs of rain. It’s important to be prepared for flooding no matter where you live, but particularly if you are in a low-lying area, near water or downstream from a dam. Even a small stream or dry creek bed can overflow and create flooding.

Important information regarding flooding is available at NOAA’s Flood Safety website.

Flooding at Walmart in Seaford, DE

Terms used to identify the severity of a flood

  • Flood Watch: Flooding is possible. Tune in to NOAA Weather Radio, commercial radio, or television for information.
  • Flash Flood Watch: Flash flooding is possible. Be prepared to move to higher ground; listen to NOAA Weather Radio, commercial radio, or television for information.
  • Flood Warning: Flooding is occurring or will occur soon; if advised to evacuate, do so immediately.
  • Flash Flood Warning: A flash flood is occurring; seek higher ground on foot immediately.

Preparing your home

  • Research and purchase flood insurance. Homeowners’ insurance does not cover flooding. Note that many flood insurance policies take at least 30 days to go into effect.
  • Elevate the furnace, water heater, and electric panel in your home if you live in an area that has a high flood risk.
  • Consider installing “check valves” to prevent flood water from backing up into the drains of your home.
  • If feasible, construct barriers to stop floodwater from entering the building and seal walls in basements with waterproofing compounds.

Stay safe around flooding

  • If water has entered a garage or basement, do not walk through it. It may contain hazardous materials.
  • Do not try to drive over a flooded road. If your car stalls, abandon it immediately. Attempting to move a stalled vehicle in flood conditions can be fatal.
  • Do not walk through moving water. Six inches of moving water can make you fall. If you must walk in water, walk where the water is not moving. Use a stick to check the firmness of the ground in front of you.
  • Stay clear of water that is in contact with downed power lines.
  • Do not allow children to play around high water, storm drains, or any flooded areas.
  • If you are asked to leave your property, disconnect all electrical appliances and shut off electric circuits. If advised by your local utility, shut off gas service, as well.

Planning for evacuation

  • If you feel that you will be in danger, evacuate!
  • If you have pets or farm animals, take them with you or make appropriate arrangements for them to stay far away from potential flood danger.


Though Delaware has never experienced a direct hit from a hurricane, it has experienced some of the most powerful parts of nearby storms. Hurricane hazards include storm surge and severe coastal flooding, high winds, inland flooding, tornadoes, and large waves and rip currents.

Check out the NOAA National Hurricane Center for current tropical storm and hurricane conditions and important educational information:

Hurricane Isabel in 2003.

Terms used to identify the severity of a hurricane

  • Tropical storm: Maximum sustained surface wind speed using a one-minute average of 39 to 73 mph.
  • Hurricane (also known as a typhoon or a cyclone): Maximum sustained surface wind speed using a one-minute average of more than 74 mph.
  • Tropical Storm or Hurricane Watch: Sustained winds of the relevant category or higher are possible within the specific area. Usually issued 48 hours in advance of the area being hit by the storm force winds.
  • Tropical Storm or Hurricane Warning: Sustained winds of the relevant category or higher are expected shortly to affect the specific area. Usually issued 36 hours in advance of the area being hit by the storm force winds.
  • Severity of hurricanes is rated according to the Saffir-Simpson Hurricane Scale:
    • Category 1: 74 to 95 mph with dangerous winds that will cause some damage.
    • Category 2: 96 to 110 mph with dangerous winds that will cause extensive damage including major roof and siding damage.
    • Category 3: 111 to 129 mph with dangerous winds that will cause devastating damage including removal of roof and decks. Electricity and water unavailable for several days to weeks.
    • Category 4: 130 to 156 mph with dangerous winds that will cause catastrophic damage including most of roof structure and some exterior walls, uprooted trees, downed power lines, and power outages that can last weeks or months.
    • Category 5: 157 mph or higher with dangerous winds that will cause catastrophic damage including total destruction of built structures, total roof failure, and wall collapses. The area will be uninhabitable for weeks or months.

Preparing your home

  • Cover all windows with pre-cut plywood or hurricane shutters to protect from high winds.
  • Plan to bring in all outdoor furniture, decorations, garbage cans, and anything else that is not tied down.
  • Keep all trees and shrubs well trimmed to reduce potential debris.
  • Secure your home by closing shutters and securing outdoor objects or bringing them inside.
  • Turn off utilities as instructed. Otherwise, turn the refrigerator thermostat to its coldest setting and keep the door closed.
  • Turn off propane tanks.
  • Ensure a supply of water for sanitary purposes such as cleaning and flushing toilets. Fill the bathtub and other large containers with water.

Planning for evacuation

Winter Storms

Nor’easters are winter storms that move north up the East Coast of the United States. Severe nor’easters can bring high winds, heavy precipitation, and low temperatures. The National Weather Service refers to winter storms as “Deceptive Killers” because most deaths are indirectly related to the storm. Instead, people die in traffic accidents on icy roads and of hypothermia from prolonged exposure to cold. It is important to be prepared for winter weather before it strikes.

Stay off the roads until they have been cleared, especially if a snow emergency has been issued. If you must travel by car, carry an emergency supply kit in the trunk. Keep your car’s gas tank at least half full. Let someone know your destination, route, and when you expect to arrive. If your car gets stuck along the way, help can be sent along your predetermined route.

Don’t forget your pets and farm animals!

Important information is available at NOAA at this link.

Georgetown in 2010.

Terms used to identify the severity of a winter storm

  • Freezing rain: Creates a coating of ice on roads and walkways.
  • Sleet: Rain turns to ice pellets before reaching the ground. Sleet also causes roads to freeze and become slippery.
  • Winter Weather Advisory: Cold, ice, and snow are expected.
  • Frost/Freeze Warning: Below freezing temperatures are expected.
  • Winter Storm Watch: Severe weather such as heavy snow or ice is possible in the next day or two.
  • Winter Storm Warning: severe winter conditions have begun or will begin soon.
  • Blizzard Warning: Heavy snow and strong winds will produce a blinding snow, near zero visibility, deep drifts, and life-threatening wind chill.

Preparing your home and your vehicle

  • Add the following supplies to your disaster kit in preparation for winter weather:
    • Rock salt to melt ice on walkways or sand to improve traction
    • Snow shovels and other snow removal equipment
    • Adequate clothing and blankets to keep you warm
  • Hire a contractor to check the structural stability of the roof to sustain unusually heavy weight from the accumulation of snow or water if drains on flat roofs do not work.
  • If you have a car, fill the gas tank in case you have to leave. In addition, check or have a mechanic check the following items on your car:
    • Antifreeze levels – ensure they are sufficient to avoid freezing.
    • Battery and ignition system – should be in top condition and battery terminals should be clean.
    • Brakes – check for wear and fluid levels.
    • Exhaust system – check for leaks and crimped pipes and repair or replace as necessary. Carbon monoxide is deadly and usually gives no warning.
    • Fuel and air filters – replace and keep water out of the system by using additives and maintaining a full tank of gas.
    • Heater and defroster – ensure they work properly.
    • Lights and flashing hazard lights – check for serviceability.
    • Oil – check for level and weight. Heavier oils congeal more at low temperatures and do not lubricate as well.
    • Thermostat – ensure it works properly.
    • Tires – make sure the tires have adequate tread. All-weather radials are usually adequate for most winter conditions. However, some jurisdictions require that to drive on their roads, vehicles must be equipped with chains or snow tires with studs.
    • Windshield wiper equipment – repair any problems and maintain proper washer fluid level.


Tornadoes are nature’s most violent storms. Planning and practicing specifically how and where you take shelter could save your life. Be prepared to act quickly.



Terms used to identify the severity of a tornado

  • Tornado Watch: Prepare yourself! A tornado is possible in or near the watch area. Watch areas are identified by county.
  • Tornado Warning: Take Action! A tornado has been sighted in your area. Warnings are also identified by city area or region of a county.

2004 tornado in New Castle, DE

Preparing your home

  • Some important tips for preparing yourself and your homes for tornadoes can be found at the NOAA website.
  • Find out what kinds of warning and alert systems your community uses: sirens, media, or smart phones.

Additional resources