What is a Derecho?
A derecho is a large, fast-moving band of thunderstorms producing straight-line winds of at least 58 mph (93 km/h) sustained along a path over 240 miles (about 400 km) long, with gusts often exceeding 75 mph and sometimes reaching hurricane force (over 100 mph). Unlike tornadoes, whose winds spin, derechos produce winds that blow in a straight, intense line, causing widespread damage in their path. Because of their sheer scale, derechos can travel hundreds of miles in just a few hours, leading to extended periods of devastation.
This storm type is sometimes called an “inland hurricane” due to its powerful, hurricane-force winds and potential to knock down trees, power lines, and structures over vast areas. Derechos typically occur during warm months—mostly June through August in the Northern Hemisphere—when conditions support clusters of intense thunderstorms moving rapidly in a bow-shaped line formation.
Current Derecho threat and forecast
Severe weather warnings have been issued for parts of South Dakota, Iowa and Minnesota, where the National Weather Service’s Storm Prediction Center has assigned a Level 4 out of 5 risk, signaling a high probability of dangerous storms. Residents can expect sustained damaging winds upto 90 mph, with occasional localized gusts potentially higher.
How to stay safe during a Derecho
Due to the rapid onset and destructive nature of derechos, the National Weather Service and experts advise taking severe thunderstorm warnings seriously and adopting precautions similar to those for tornadoes:
- Seek shelter indoors immediately—preferably in a basement or an interior windowless room such as a bathroom or closet.
- Stay away from windows and exterior doors to avoid injury from flying debris.
- Charge all mobile devices beforehand to maintain communication during potential power outages.
- Have multiple ways to receive weather alerts—don’t rely solely on cellular service, as it can be disrupted. NOAA Weather Radio or local radio stations are critical sources.
- Avoid travel during storm warnings, as strong winds can make driving hazardous.
- Secure outdoor objects that can become deadly projectiles in high winds.
Meteorologists emphasize that the defining danger of derechos comes from sustained, intense wind gusts that can cause structural damage and widespread power loss rapidly over large regions.
Why Derechos are so destructive
Derechos form as clusters of thunderstorms known as mesoscale convective systems. These storms develop bow-shaped radar signatures (“bow echoes”) due to strong winds pushing out rain-cooled air ahead of them. This creates gust fronts of extremely fast winds that spread damage over a linear swath hundreds of miles long.
The intensity and speed of these winds mean entire forests can be flattened, crops severely damaged, and urban infrastructures severely impacted in minutes. Unlike tornadoes, which affect smaller areas, derechos bring a broad corridor of destruction across multiple states or regions.Residents in the northern Plains and Upper Midwest should monitor official weather sources closely and prepare for possibly days without power or normal services. Prompt action and preparedness remain the best defense against the rare but devastating derecho storms.
