Sometimes referred to as a "wall of wind" or even the "horizontal tornado", derecho means "straight line" in Spanish. It's a reference to their immense bow, hundreds of kilometres long.
Whatever you call them, you don't forget an encounter with a derecho in a hurry.
"They tend to be very fast moving, the 2012 event was a continuous line moving at 100km/h and once that boundary hits you the winds dramatically increase and become violent even though before they may have been quite light," says Dean Sgarbossa, an extreme weather expert with the Bureau of Meteorology, who has seen a derecho up close.
He tells news.com witnessing a derecho is "confronting but awe inspiring."
As the sun began to set on that hot and steamy June day in 2012, few of the millions of people along the derechos soon-to-be -path-of-rampage were concerned. Notoriously hard to predict, up until early evening only a "low threat" of thunderstorms was predicted.
But it was bubbling up from a well of storms near Chicago. From there a solid band of storms 160km wide, would barrel through Indianapolis, Cincinnati, Pittsburgh, and DC.
The US' national weather service would later go onto to describe the storm as "historic" due to its widespread path of destruction.
As well as the scores killed in smashed houses or by falling trees; five million were left without power and billions of dollars of damage was caused in the derechos wake.
"Nobody had any warning. It defied all weather models, and no utility was prepared for it," Jerry Pasternak, an executive with energy utility Pepco told Washington radio station WTOP this week.
"It was one of the worst storms we had, as far as how quickly it came up," Baltimore resident Melissa Kitner-Triolo told the Baltimore Sun.
"It was the wind more than anything. At first, you didn't hear the rain so much. It was like a microburst. It was pretty terrifying."
Mr Sgarbossa describes a derecho as a continuous line of intense thunderstorms; a widespread and long lived wind storm with bands of rapidly moving showers.
Only two or three year form in the US annually.
"For a derecho to develop, it needs quite specific atmosphere conditions. Humidity leading to unstable conditions promoting thunderstorms; a low pressure trough or cold front and you also need what we call vertical wind shear which separates rising warm humid air and descending cooler air and that makes that continuous line."
It's the sheer size of this line of storms that makes derechos so destructive. Yet the winds speeds are usually far below that of a tornado which typically spin at around 500km/h.
"A tornado might only be a few hundred metres in length. But derechos have an almost continuous line of winds of 90 to 120km/h and that's when you start to get structural damage, uprooting of tree roots and houses roofs," says Mr Sgarbossa.
With tornadoes embedded with derechos this can cause even greater, localised, damage.
Mr Sgarbossa came face-to-face a derecho like storm with winds of more than 130km/h.
"If you know what you're looking for you can see them," he says.
Barrelling along as fast as speeding car, first a layer of red and brown haze becomes visible on the horizon as dust, debris and insects are blown ahead of the derechos bow.
"You see a shelf cloud moving towards you, so called because it looks like stacked plates, and its often dark and grey," he says.
'But as it nears you can hear that rumbling and that becomes a roaring sound. The sound is like a distant freight train approaching.
"The thunderstorms and lightening become more noticeable but the sound is drowned out by the fierce and angry wind.
"If you're standing outside, it feels like you're being sandblasted; it rains almost horizontal, street signs are swaying and knocking about, tree branches blow across the road. But it's the constant roar of the wind which is most noticeable," says Dr Sgarbossa.
"They're intimidating, confronting and exciting but awe inspiring."
Most Australians have never heard of a derecho but don't be lulled into thinking these are the one storm we don't get. We do.
"In Australia, we don't have as rigorous a derecho definition as the US but we do have similar widespread long-lived windstorms with rapidly moving thunderstorms - we know them as squall lines," he says.
Indeed one passed over Adelaide on 19 January.
"It was in excess of 100kms long, started over the Yorke Peninsula then entered Adelaide and produced damaging wind gusts 111kms at Adelaide airport."
Some damage was done, but far less than the 2012's deadly derecho over DC.
With less measuring stations than the US, and vast tracts of sparsely populated land, its possible Australia has derechos darting about the outback that few even see.
The US derecho was said to be the largest non-hurricane related outage in the country's history. It took 10 days for some homes to be reconnected to the grid.
Climate scientists aren't convinced a warming planet will make derechos any stronger or more frequent. But they do warn that as once temperate areas become more humid, the deadly storms could shift further north in the US.
Here in Australia, that could mean that Adelaide's derecho this year, could be Melbourne's in the coming future.
