Spring & Summer Severe/Hazardous Weather Terms

Hazardous weather that most affects the state of Ohio during spring and summer months includes thunder, lightning and hail storms, tornadoes, floods and extreme heat. The following severe weather terms are defined by the National Weather Service.

The National Weather Service (NWS) is responsible for issuing severe weather watches, warnings and advisories to alert the public when dangerous weather conditions are expected.

  • Watch - A weather watch means the potential or conditions exist for a dangerous weather event.
  • Warning - A weather warning means that a dangerous weather event is imminent. Immediate action must be taken to protect life and property.
  • Advisory - A weather advisory means a less dangerous weather event is imminent and is less severe than a warning. However, a hazardous weather event is still threatening to occur.

Hazardous Weather Outlook - A hazardous weather outlook is given when forecasters believe significant weather conditions are possible. An outlook is usually issued 24-72 hours in advance of an event.

Special Weather Statement – Provides the public with information concerning ongoing of imminent weather hazards, including strong storms that may become severe.

Short Term Forecast - A short-term forecast describes the weather in the local area and includes a short-range forecast (usually not more than six hours). This product will be updated more frequently when it is used during active weather. A short-term forecast is sometimes referred to as a "NOW-cast."

Heat Index (Apparent Temperature) - A number in degrees Fahrenheit that indicates how hot it feels when relative humidity is considered along with the actual air temperature. Exposure to direct sunlight can increase the heat index by 15 degrees.


  • A weather watch means the potential or conditions exist for a dangerous weather event.
  • Action: Prepare for the weather event; listen for additional information, including warnings. Be ready to act if hazardous weather is observed.

Excessive Heat Watch - An excessive heat watch is issued when excessive heat is possible. Heat indexes are forecast at 105 degrees or higher for a period of two hours or more.

Fire Weather Watch - A fire weather watch is issued when there is the possible development of conditions favorable for forest, grass or brush fires and the conditions support extreme fire danger and/or fire behavior.

Flood Watch - A Flood Watch can be issued for several different reasons. The watch may be issued for the potential of rapid flooding from either torrential downpours, dam breaks, or ice jam breaks. A flood watch may also be issued when the onset of flooding is much slower, usually greater than six hours. The body of the watch describes what type of flooding to expect. The watches are usually issued up to 12 hours prior to the possible flood event.

High Wind Watch - A high wind watch is issued when there is a potential for dangerous winds.

Severe Thunderstorm Watch - A severe thunderstorm watch outlines an area where hail up to 1 inch in diameter or larger, and/or damaging thunderstorm winds are expected to occur. Tornadoes may be possible. In rare situations, the enhanced wording, "this is a particularly dangerous situation" will be used to describe extreme thunderstorm activity.

Tornado Watch - A tornado watch outlines an area where large hail and damaging wind threats, as well as the possibility of multiple tornadoes are possible. In rare situations, the enhanced wording, "this is a particularly dangerous situation" will be used when long-lived, strong and violent tornadoes are possible.


  • A weather warning means that a dangerous weather event is imminent. Immediate action must be taken to protect life and property.
  • Action: Take action immediately to protect life and property.

Excessive Heat Warning - An excessive heat warning is issued when heat indexes will generally reach 105 degrees or higher for a period of two hours or more.

Flash Flood Warning - A flash flood warning signifies a short duration of intense or rapid flooding of counties, communities, streams, or urban areas. Flash floods may result from such things as torrential downpours, dam breaks, or ice jam breaks.
Action: Take action immediately - move to higher ground, do not drive through flooded roadways.

Flash Flood Statement - A flash flood statement provides supplemental information on active Flash Flood Warning products, such as updated observations and impact information. It will provide the latest information on the flash flooding situation or event.

Areal Flood Warning – An areal flood warning may be issued for any high flow, overflow, or inundation in a geographical area which threatens life and property and isn’t appropriately covered by a flash flood warning or flood warning for forecast points.

Flood Statement - A flood statement is issued after a Flood Warning. It will provide the latest information on the flooding situation or event.

High Wind Warning - A high wind warning is issued when sustained winds are predicted to reach 40 mph or greater for at least one hour, or any gust of wind is expected to be 58 mph or greater.

Severe Thunderstorm Warning - A severe thunderstorm warning is issued when large hail or damaging wind is actually occurring or imminent. Severe thunderstorms can produce tornadoes with little or no advance warning. Severe thunderstorms will also produce frequent and dangerous lightning.
Action: Seek safe shelter immediately. Criteria: Hail - 1" or larger; Wind - 58 mph or greater.

Severe Weather Statement - A severe weather statement provides follow-up information on severe weather conditions (severe thunderstorm or tornadoes) which have occurred or are currently occurring.

Special Marine Warning - A special marine warning is issued for any of the hazardous maritime weather conditions; thunderstorms over water; thunderstorms that will move over water; or waterspouts which usually last two hours or less and produce sustained winds or frequent gusts of 34 knots or more, and/or hail ¾ inch or larger. The Special Marine Warning should also be issued for non-convective short duration winds of 34 knots or greater.
Action: Boaters should move to safe harbor.

Red Flag Warning - A red flag warning is issued when extreme burning conditions are forecasted. Forecasting criteria includes relative humidity, wind and temperature. Dry fuels are also a factor.
Action: No open burning.

River Flood Warning - A river flood warning is issued for specific communities or areas along a river where flooding is imminent or occurring. River flood warnings will provide crest forecasts.
Action: move to higher ground; do not drive through flooded roadways

Tornado Warning - A tornado warning is issued if a cloud rotation has been spotted or when a tornado is imminent or occurring. This includes when a tornado is indicated by Doppler radar or sighted by spotters.
Action: Seek safe shelter immediately.


  • Advisories are for conditions less serious than warnings, and cause significant inconvenience. If caution is not exercised, weather advisories could lead to situations that may threaten life or property.

Dense Fog Advisory - A dense fog advisory is issued when widespread fog will reduce visibility to one-fourth mile or less.

Heat Advisory - A heat advisory is issued when heat index is expected to reach at least 100°F but less than 105°F

Urban & Small Stream Flood Advisory - An urban and small stream flood advisory provides information on elevated river/stream flow or ponding of water in geographical area when such an event warrants notification of the public in a product less urgent than a warning. This advisory is issued when heavy rain is predicted to cause flooding of streets and low-lying places in urban areas. It is also used if small rural or urban streams are expected to reach or exceed their banks.

Wind Advisory - A wind advisory is issued when sustained winds are expected to be 40 mph or greater for at least an hour, or any wind gust between 46 mph and 57 mph.


Cold Air Funnels
Weak funnel cloud extensions from cumulous clouds that typically remain aloft. Cold air funnels form in cold, unstable air masses and are not usually associated with thunderstorms or severe weather.

A strong downdraft current of air from a thunderstorm, often associated with intense thunderstorms. Downbursts may produce damaging winds at the surface.

Flash Flood
A rapid and extreme flow of high water into a normally dry area, or a rapid rise in a stream or creek above a predetermined flood level, beginning in a short period of time from the causative event. A flash flood can occur very rapidly. Flash floods occur as the result of very heavy rainfall in a short period of time, generally over a relatively small area.

A condition that occurs when water overflows the natural or artificial confines of a stream or body of water, or accumulates by drainage over low lying areas. This flood is any high flow of water, overflow, or inundation by water which causes or threatens damage.

Funnel Cloud
A condensation funnel extending from the base of a towering cumulus cloud associated with a rotating column of air that is not in contact with the ground – and hence, different from a tornado. A condensation funnel is a tornado, not a funnel cloud if
a.) it is in contact with the ground;
b.) a debris cloud or dust whirl is visible beneath it.

Gust Front
The leading edge of gusty surface winds that flow from the base of a thunderstorm and spread along the ground in advance of the thunderstorm.

A visible electrical discharge produced by a thunderstorm. The discharge may occur within or between clouds, between the cloud and air, between a cloud and the ground or between the ground and a cloud.

Severe Thunderstorm
A thunderstorm producing a tornado and/or, damaging winds of 58 mph or higher, and/or hail 1 inch in diameter or larger.

Squall Line
A line of active thunderstorms, either continuous or with breaks, including contiguous precipitation areas resulting from the existence of the thunderstorm.

Straight-Line Winds
Generally, any wind that is not associated with rotation, used mainly to differentiate them from tornadic winds. These thunderstorm winds may produce damage that typically exhibits a lack of a rotational damage pattern.

In general, a local storm produced by a cumulonimbus cloud, and accompanied by lightning and thunder, many times with strong wind gusts, heavy rain and sometimes hail. A cumulonimbus cloud is a cauliflower-shaped cloud that usually has a height taller than or equal to its width.

A violently rotating column of air that comes in contact with the ground, usually, descending from the base of a thunderstorm. In Ohio, many tornadoes are obscured by hills, trees and rain.

SOURCE:  Ohio Committee for Severe Weather Awareness