While the peak occurrences for severe weather events in the United States happen between March and October, severe weather can occur at any time. In order to save lives, branches of the National Oceanic and Atmospheric Administration (NOAA) will issue public watches and warnings.
Knowing the difference between the two can prepare individuals for the necessary steps to take when considering the threat of severe weather. Watches and warnings issued to the public are based on different criteria.
"A watch is issued when conditions are favorable, for example, either for a severe thunderstorm or tornadoes," AccuWeather.com Senior Meteorologist Dan Kottlowski said. "It doesn't mean severe weather is imminent."
"Typical watches cover about 25,000 square miles, or about half the size of Iowa," according to the SPC.
Kottlowski said there are no set criteria for issuing watches, but if the conditions seem consistent with a developing severe weather pattern, watches can be changed and altered by monitoring ongoing developments.
"It can vary," he said. "There is not just one set of ingredients; every watch may have a different set of perimeters from one day to the next since it is based on a synoptic situation that may change within several hours."
Warnings mean that severe weather is imminent and is based on specific criteria and existing reports received by the NWS.
The criteria include hail that totals more than 1 inch in diameter and wind speeds of 55 mph.
"Lightning is not a criteria for a severe thunderstorm warning," Kottlowski said. "Heavy rain is not either."
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Warnings must follow the two main criteria, he said, adding urban flood and stream advisories, flash flood watches and warnings, and flood watches and warnings, may accompany a storm with heavy rain.
Warnings are issued through the efforts of individuals working for the NWS.
"The way a warning is issued is that a meteorologist will monitor the weather by radar and look for particular areas where there could be high impact damage," Kottlowski said. "They will issue a warning and there will be a signature for an existing storm or developing tornado."
Trained NWS spotters will verify reports of rotation or storm damage.
"This gives the meteorologists confidence in what they are seeing on radar," he said.
Those looking for a break from the heat across the central United States will be in luck as a slow cooldown is in store starting this weekend.
The midwestern United States will be in the crosshairs of potent thunderstorms into Saturday night.
Much of the eastern United States will continue to swelter with above-average temperatures into the end of the month.
Conditions will deteriorate across Hawaii this weekend as Darby delivers locally heavy rain and rough surf. But the tropical storm will provide long-term benefits.
Stifling heat has been baking the central United States but will finally ease across northern areas this weekend.
Lightning killed a teenager on Friday, the second teen lightning death in three days. With thunderstorms continuing to rattle several parts of the nation, more lives will be at risk.
Mid-Atlantic Ocean (1788)
(22nd-24th) George Washington Hurricane; After causing ship disasters off SW Bermuda, the storm moved NW over Tidewater, NC and VA to pass right over George Washington's Mt. Vernon plantation. On July 24th, George Washington wrote in his diary: "About noon the wind suddenly shifted from NE to SW and blew the remaining part of the day violently from that quarter. The tide this time rose near higher than it was ever known to do, driving boats, etc. into fields, where no tide had ever been heard of before, and most, it is apprehended, having done infinite damage on their wharves at Alexandria, Norfolk, Baltimore, etc. At home all day."
Canton, IL (1975)
A tornado ripped through a 3-block section of downtown, killing 2 people, injuring 75 and creating $5 million damage. A 15-foot wooden plank was driven through an auto engine block, splitting the front of the car in two. The woman driving was not injured. National Guardsmen were called in to prevent looting.
Columbus, OH (1979)
This is the first year in 101 years of record keeping at Columbus in which the temperature has not reached 90 degrees by July 23rd.