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While tornado season is said to fall between March and June, they can happen anytime depending on where you live.

It’s for this reason that you should know the signs of a tornado and how to quickly find emergency shelter.

Tornado Warning: Quick Reference Guide

  • A dark, often greenish, sky
  • Wall clouds
  • Large, heavy hail often without any rain
  • A sudden die down of wind – also the air may become very still
  • A loud roar similar to a freight train may be heard
  • A cloud of dust and debris approaching, with or without a visible funnel
  • Keep on Hand: Tornado or Hurricane Survival Kit

Video: Tornado Spotting – What to Look For

What is a Tornado?

A tornado is a fast-spinning platoon of air that’s in association with a cumulonimbus cloud and the surface of the earth.

Sometimes it can even be in contact with the cumulus cloud base – though this is rare.

Many times, a windstorm is called a cyclone, whirlwind, or twister. It’s worth noting though that the term cyclone is usually used in meteorology to define a weather system that has a low-pressure area along the center.

If someone was looking towards the earth’s surface they would likely see the winds blowing clockwise in the Southern Hemisphere and counter clockwise in the Northern Hemisphere.

Tornadoes come in various sizes and shapes and many of them come with wind speeds of up to 180 km/hr and are approximately 80 feet across.

Note, during a tornado, it’s important to have emergency water storage on hand and, if water does end up being scarce, that you watch for symptoms of dehydration.

More helpful reading:

Where are Tornadoes Most Prevalent?

For home base, tornadoes occur more often in Northern America than the southeastern and central regions in the United States, and is commonly known as tornado alley.

They are also likely to occur in southeast and northwestern Europe, southern Africa, Southeastern and Western Australia, Southeastern America, Bangladesh, New Zealand, and Eastern India.

Meteorologists are experienced enough to detect the warning signs of a tornado and utilize a Pulse-Doppler radar which monitors reflectivity data and velocity patterns – such as debris balls or hook echoes.

They also leverage storm spotters to watch for signs and alert people of the news.

How Long Do Tornadoes Last

On average, most tornadoes will last under 10 minutes, but they can be live more than an hour at a time and have been known to appear briefly for just a few seconds.

What Causes Tornadoes?

Some of the most aggressive tornadoes originate from supercells.

These can be defined as big thunderstorms (and lightning) with revolving winds. Approximately one in one thousand storms will become a supercell, and one in every five or six supercells generates a tornado.

Often, the states lying near the Gulf of Mexico will experience the tornado warning season at the onset of spring.

More tornadoes usually occur during the month of May even though April has the most turbulent twisters. Tornadoes can occur both during the day or night but many of them form in the afternoon when the ground is sufficiently hot to generate thunderstorms.

What are the Signs of a Tornado Coming?

We’ll look at the signs of a tornado forming more comprehensively later in this article.

First, let’s look at how they begin, and then we’ll look at the stages of a tornado.

Tornadoes occur when humid and warm air crashes with dry and cold air. The solid cold air is thrust through the warm air often resulting in thunderstorms. The warm air then advances over the cold air and triggers an updraft.

The updraft then starts to revolve in cases where winds sharply differ in terms of direction and speed. The revolving updraft is known as a mesocyclone, and the revolving speed accelerates as it gathers more warm air from the advancing thunderstorm.

Watch out for these Signs of a Tornado Forming

Cool air delivered by a strong line of wind in the air supplies more energy. The moist air from the mesocyclone forms water droplets which eventually results in a funnel cloud.

The funnel grows continuously and later descends from the cloud base. The moment it gets into contact with the ground, a tornado is likely to occur.

Types of Tornadoes

Two types of thunderstorms usually trigger tornadoes.

They are:

  • Non-supercell

  • Supercell

The most common (and typically dangerous) tornadoes originate from a supercell.

A revolving updraft, also is known as a mesocyclone, plays a major role in the occurrence of a supercell and ultimately a tornado.

There are various ways within which rotation can occur. The first one involves a wind shear.

This occurs when winds from two varying levels aloft the ground blow in varying directions and at varying speeds.

How a Wind Shear can Trigger the Warning Signs of a Tornado

Wind shear is likely to trigger a tornado if the winds at the ground level, usually moderated by irritation with the surface of the earth, originate from the southwest side at 5mph.

If at 500 feet high above the same area the winds are storming from the southeast at approximately 25 mph, a microscopic line of air starts to revolve horizontally.

Ascending air in the thunderstorm raises the rotating air to a vertical position and eventually, the rotation area develops throughout a large portion of the storm.

A tornado is likely to form when the updraft is rotating and receiving warm and moist air at ground level.

How fast do tornadoes move?

Tornadoes generally average about 30 mph and can go as fast as 70 mph.

What do Scientists think?

If you asked any scientist, they probably will tell you they’re still studying the occurrence and have much to learn.

Many scientists have yet to feel they truly understand tornadoes and have lingering questions – especially since 20% of all supercell thunderstorms are highly likely to trigger tornadoes.

Some of the lingering questions include:

  • How is it possible that one supercell thunderstorm can trigger a tornado while a similar storm doesn’t?
  • Could there be other circulation causes for tornadoes?
  • What triggers winds moving in varying directions or speeds that trigger the rotation?
  • What’s the function of downdrafts and the circulation of moisture and temperature in tornado genesis?

Now that we understand that all tornadoes don’t result from supercells, what are the warning signs of tornadoes which occur in non-supercell thunderstorms?

Understanding Non-Supercell Tornadoes

Non-supercell tornadoes don’t occur from coordinated storm-scale rotation.

They form from a vertically rotating pack of air presently occurring close to the ground triggered by wind shear from a cold, warm, or even sea breeze front, and sometimes a dry line.

In the event that an updraft maneuvers across the rotation to expand it, a tornado is highly likely to occur.

Often, non-supercell tornadoes occur in scarcely populated areas – which is why scientists can’t tell their magnitude.

However, they’re often small.

Establishing the Signs of a Tornado

As we’ve already mentioned above, tornadoes often occur during the day and many times in the afternoon.

But, they can happen both during the day and night which is why you should beware of the signs of a tornado at night.

Often, tornadoes will move swiftly from the southwest towards the northeast.

However, they can still move in any other direction.

A tornado can linger in the ground for approximately 20 minutes and may also make contact with the ground at various times – often in different areas.

Here are warning signs you should look out for.

1. A Funnel-shaped cloud

What do clouds look like before a tornado?

A funnel-shaped cloud is probably one of the surest indications of a tornado.

It’s important to note that the cloud won’t resemble normal clouds you would see in the sky on a typical day.

The funnel-shaped cloud is usually very large and looks like the image below.

And, if you take a closer look you’re likely to see it rotating and escalating from a prevailing storm you can see approaching the ground.

funnel shaped cloud

Perhaps you’re already aware that tornadoes originate or even form in one place and how you’re likely to spot a funnel-shaped cloud forming.

During a tornado, the weather is likely to get rough – and strong – causing the sky to grow extremely dark.

If you’re caught in the melee unexpectedly and don’t have emergency shelter, cover, or a building basement available, keeping your eyes focused in the sky will help save you from injury.

2. A Huge Cloud of debris

One of the signs of a tornado coming at night is a big cloud of debris which often hides the funnel cloud.

If you notice a cloud of debris even when the funnel cloud isn’t visible, it may be wise to find an escape route as fast as possible to an emergency shelter (preferably with power) – this is one of the biggest tornado warning signs.

3. A Loud Blast in the Sky

If you hear an unusual blast in the sky, it’s another one of the common warning signs of a tornado. Again, it may sound similar to a freight train.

The blast can be tremendous and frightening to both adults and children.

Unlike thunderstorms, a tornado blast is continuous like a freight train and emanates from the sky.

Listen to see if the sounds of the loud blast increase as the tornado is coming.

Often, this noise will be accompanied by strong winds which can indicate a robust and dangerous disaster. If this happens, look for an emergency building to stay in.

Video: What does a tornado sound like

Tornado sounds: Clear sound of a large roaring Tornado

4. Calmness After a Thunderstorm

If you notice an unusual calm in the conditions preceding a storm, that could also be signs of a tornado approaching.

In this case, you may want to prepare yourself accordingly and find an emergency shelter in a safe place.

While it’s normal for skies to clear after a storm, you should be alert when there’s a strange serenity in the atmosphere.

5. A Blackish Green Colored Sky

During a storm, the sky often becomes blackish.

However, one of the common signs of a tornado at night is when the sky changes to a blackish green color.

This can indicate a huge storm accompanied by clouds and strong winds from where a tornado could occur – especially at night.

You can see the hue in this picture below.

Why does the sky turn green before a tornado?

Experts aren’t quite sure, but it’s thought that because of the golden and red hues from sunsets and the blue that occurs in the air from scattered light molecules that they combine and give us the green colored sky.

Green sky tornado

blackish green colored sky sign of a tornado

6. Debris Falling from the Sky

Another of the warning signs of a tornado is debris falling from the sky.

Usually, a tornado comes with strong winds which pick up flying debris and deposit it miles away.

Sometimes the strong winds generate strange roaring sounds.

What to do if a Tornado is Coming

During a tornado watch, if you notice falling debris from clouds in the sky, don’t stay where you are at. You need to look for a safe hiding place to stay at like the interior of an emergency shelter – preferably that has power – cover, or the basement of a house or building.


When the weather is favorable for a tornado to occur,  the meteorological and weather service department in various tornado-prone areas usually release a tornado watch via news or radio with warnings to stay inside.

Once the tornado shows up on the radar, a tornado warning is issued.

If you or your family live in areas where tornadoes occur frequently, be on the watch just to be safe.

More helpful reading:

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