When is wind strong? – A look at the Beaufort scale

Wind exists in many variations. Sometimes, there is a lot of wind – whether that’s wind gusts or average winds, like in situations where it’s stormy. On other occations, there is absolutely no wind. Funnily, there is an interesting reason as to why that’s the case.

It’s all related to areas of high pressure and low pressure. With a high pressure area, often, there is not much wind. Low pressure areas, more specifically depressions and stronger storms, often come with more wind. Hurricanes are the strongest of storms that we know on our planet.

But what does it mean when there’s “no wind”? When’s the wind moderately strong, or perhaps even gale force? What wind speeds equal storm force? And hurricane force? That’s the scope of today’s weather article – answering the question when is wind strong?

For doing so, we’ll first take a look at a scale for expressing wind force – the Beaufort scale. Subsequently, we’ll cover all numbers on the scale, and show what the weather is like when that wind happens. As we do so with comparative pictures taken at sea, you can also visualize the strength of the wind that we describe. Finally, we provide a brief recap.

Ready? All right, let’s take a look! 🙂

Disclaimer: all images used in this article are licensed to be in the public domain, except for the image above, which is licensed according to the Pexels License. We thank the photographers for creating the pictures, as they are highly beneficial to our article.

Introducing the Beaufort scale

Now, as we said, we’ll be taking a look at what is known as the Beaufort scale or Beaufort wind scale. We must do so before we can categorize wind speeds; there are no categories without a scale, are there?

In meteorology, the Beaufort wind scale is used to determine the so-called “wind force”, and represents a categorization of wind speeds into a categorie that describes the strength of the wind.

Originally, an Irishman came up with this scale to measure wind at sea – and was meant for the shipping business. However, when they started to use the scale, it turned out to be used so often that it was adapted for everyday use. In fact, the British navy eventually required navy ships to use the scale to communicate about winds during inter-ship communication.

The scale represents thirteen wind categories, represented by the Beaufort numbers 0 (calm wind) to 12 (hurricane force winds). Before we’ll cover them in more detail, we’ll present them first:

  • 0: Calm
  • 1: Light air
  • 2: Light breeze
  • 3: Gentle breeze
  • 4: Moderate breeze
  • 5: Fresh breeze
  • 6: Strong breeze
  • 7: Moderate wind
  • 8: Gale
  • 9: Strong gale
  • 10: Storm
  • 11: Violent storm
  • 12: Hurricane force

Now, it’s time to look at each wind category and see what the weather is like then!

Beaufort number 0: calm

0-1 knots, 0-1 mph, 0-2 km/h, 0-0.5 m/s

When the wind speed is less than two kilometres an hour, it’s possible to say that our atmosphere is calm – or “wind silent”, if you will. It’s impossible or barely possible to feel any wind. Anemometers at weather stations in the same region get confused when this happens, because any breeze will ensure that it moves into a particular direction, without the wind blowing from that direction from a continuous amount of time.

In short: the weather maps with current weather displays wind vanes pointing into a variety of directions in situations where the wind is calm.

At sea, the water will be like a mirror:

Beaufort number 1: light air

1-3 knots, 1-3 mph, 2-5 km/h, 0.5-1.5 m/s

When the wind speed is between two to five kilometres an hour, the Beaufort scale categorizes the wind as light air, or Beaufort scale number 1.

At sea, the wave height will be approximately 0.25 feet (or 0.1 metres), and tiny ripples will be visible. No foam can be seen.

On a chart representing actual weather, wind vanes are now all blowing from similar directions. On land, wind can barely be felt. It’s possible to feel a minor breeze only.

Beaufort number 2: light breeze

4-6 knots, 4-7 mph, 6-11 km/h, 1.6-3.3 m/s

From 6 to 11 kilometres per hour, we’re talking about a light breeze when we discuss wind speed – or Beaufort scale number 2. Waves at sea have a height of approximately 0.2 to 0.3 metres (0.5 to 1.0 feet), and have become a bit bigger compared to scale 1 force winds.

While there are small wavelets, the gulf crests do not break and have a glassy appearance. On land, we can actually feel the wind, but it’s unlikely that you’ll be thinking oh, such wind. On the contrary: hot summer days with a tiny bit of wind, that’s scale 2 force (increasing to 3-4 sometimes).

Beaufort number 3: gentle breeze

7-10 knots, 8-12 mph, 12-19 km/h, 3.4-5.5 m/s

Between 12 and 19 kilometres an hour, the wind can be said to be breezing gently. At sea, relatively large wavelets can be seen, including breaking crests – for the first time. Sometimes, a bit of white can be seen, but that will be only minor. Waves are approximately 0.6 to 1.0 metres (2.0 – 3.0 feet) high.

On land, wind can be felt clearly. Especially on the beach, those winds can be refreshing.

Beaufort number 4: moderate breeze

11-16 knots, 13-18 mph, 20-28 km/h, 5.5-7.9 m/s

Wind speeds between 20 and 28 kilometres an hour indicate Beaufort scale number 4, or a moderate breeze. At sea, small waves become longer, and include white parts (‘white horses’, according to the picture) more frequently. Waves are 1.0 to 1.5 metres (3.5 – 5.0 feet) high.

On land, especially on the beach, Beaufort scale 4 winds can mean that it’s no longer comfortable to be sunbathing, to give just one example. Scale 4 winds can be truly refreshing, which is not what you might expect from a sunny beach day. The same is of course valid for when you’re not on the beach, but the effect is a little bit less powerful there.

Beaufort number 5: fresh breeze

17-21 knots, 19-24 mph, 29-38 km/h, 8-10.7 m/s

When it’s Beaufort scale number 5, we will speak about a fresh breeze – and it happens when the wind speed is between 29 and 38 kilometres per hour. Very frequently, white foam is visible on waves when you’re at sea, including some spray. Waves themselves are 2 to 2.5 metres (6-8 feet). Don’t get wet, I’d say 🙂

On land, with Beaufort scale 5, we often feel a relatively fresh wind, that’s often strong in feeling. Usually, winds of this scale also involve slightly more intense wind gusts.

Beaufort number 6: strong breeze

22-27 knots, 25-31 mph, 39-49 km/h, 10.8-13.8 m/s

Between 39 and 49 kilometres per hour, wind is categorized into Beaufort scale number 6: a strong breeze. Waves are getting bigger slowly but surely – 3-4 metres or 9.5-13 feet – and every now and then, a larger wave becomes visible. Foam can be seen frequently.

On land, some people already have difficulty with cycling as a result of Beaufort 6 winds.

Beaufort number 7: moderate wind

28-33 knots, 32-38 mph, 50-61 km/h, 13.9-17.1 m/s

Wind speeds between 50 and 61 kilometres per hour mean that winds are moderate in Beaufort terms. The image below already writes that the “sea heaps up”, that white foam can be observed very frequently, and that parts of the waves are blown into the direction of the wind.

Waves can become approximately 4 to 5.5 metres high, or 13.5 – 19 feet.

On land, cycling gets more and more difficult, and on beaches, sand is already starting to get blown away.

Beaufort number 8: gale

34-40 knots, 39-46 mph, 62-74 km/h, 17.2-20.7 m/s

Between 62 and 74 kilometres per hour, we’re speaking about a gale in Beaufort terms. Indeed, gales are powerful winds, and at sea this has significant impact on waves. Waves at sea can become 5.5 to 7.5 metres high (18 – 25 feet), but for seamen they are only “moderately high”.

What’s more, compared to lighter winds, waves now already start to break, while foam blows into the direction of the wind.

On land, people often start complaining substantially when they face winds of Beaufort scale 8 🙂

Beaufort number 9: strong gale

41-47 knots, 47-54 mph, 75-88 km/h, 20.8-24.4 m/s

Beaufort scale force 9 means a strong gale is hitting your region. Some other countries (such as The Netherlands) already speak about a storm when this happens, so indeed, winds are quite strong to be speaking mildly. Beaufort force 9 is valid when wind speeds are between 75 and 88 kilometres per hour.

Waves at sea are approximately 7 to 10 metres high (23 – 32 feet), and indeed are high, with waves toppling more frequently.

On land, the effect cannot be ignored either. Especially when it’s summer time, and trees have a lot of leaves, the impact can be devastating – it’s not fun to have such a gale in summer. It’s likely that some trees will fall and, in densely populated countries, there will be a lot more traffic jams caused by rain related to the low pressure area.

Even far from sea, substantial wind gusts can be observed when it’s Beaufort scale 9 near the coast.

Beaufort number 10: storm

48-55 knots, 55-63 mph, 89-102 km/h, 24.5-28.4 m/s

Beaufort scale number 10 means storm. As you can see in the image below, with wind speeds between 89 and 102 kilometres per hour, waves become big. Waves of 9 to 12 metres high are common, or 29 – 41 feet. For ships, it’s no longer comfortable out there because of the shakiness, but it’s not unsafe for that matter.

On land, substantial wind gusts are more frequent than with previous wind forces.

Beaufort number 11: violent storm

56-53 knots, 64-72 mph, 103-117 km/h, 28.5-32.6 m/s

When the winds blow with speeds between 103 and 117 kilometres per hour, meteorologists classify a storm to be violent, hurricane-like (but not fully hurricane force winds yet). Waves can become 16 metres (52 feet) high, meaning that large to middle sized ships can disappear between two waves, until you pass that wave yourself.

On land, severe wind gusts can penetrate into true mainland – that is, not the coastal areas. Disruption of regular processes, such as daily commute, is common with storms like those. Often, damage yields millions of Euros in small countries, and perhaps tens of millions of Euros/Dollars in largers ones.

Beaufort number 12: hurricane force

Speeds larger than 64 knots, 73 mph, 118 km/h or 32.7 m/s

When anemometers display a Beaufort scale 12, with wind speeds equal or larger than 118 kilometres per hour, meteorologists classify windspeeds as hurricane force. While such storms do not necessarily need to be a hurricane (for example, while very rare, such wind speeds are seen in Europe as well), they’re present when hurricanes do strike.

Obviously, with very significant hurricanes, wind speeds get even larger than the speeds mentioned above; it’s the minimum level.

Hurricane-force winds are very dangerous. The sea is completely white, with very limited visibility, and extremely large waves. Ships can get into significant trouble, and unfortunately some have sunk partially as the result of such winds. Look at the picture below: waves are huge.

On land, hurricane force winds can be devastating as well. This is true for countries that are struck by hurricanes frequently, such as parts of the United States or Asia, but also for countries that aren’t. Especially in the latter category, material damages with respect to how expected such winds are, are extremely high. Unfortunately, due to sheer misfortune, people are struck personally as well, for example by collapsing trees.


In this article, we have looked at the Beaufort scale, which is used by meteorologists to classify wind speed and to give it a plainer English name. In short, we have seen that this Beaufort scale counts thirteen categories – from 0, which means that the air is calm, to 12, which means that there are hurricane-force winds.

Thank you for reading MisterWeather today. Please: if you have questions, remarks, comments or suggestions for new articles, feel free to leave a comment in the comments section below 💬 I’m looking forward to hearing from you!


Beaufort scale. (2002, December 6). Wikipedia, the free encyclopedia. Retrieved September 16, 2020, from https://en.wikipedia.org/wiki/Beaufort_scale

Francis Beaufort. (2003, September 18). Wikipedia, the free encyclopedia. Retrieved September 16, 2020, from https://en.wikipedia.org/wiki/Francis_Beaufort

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