Storm (including blizzards, dust and sandstorms)

In the Netherlands, a storm is officially defined as a period during which the average wind speed over the course of one hour reaches at least Beaufort force 9, corresponding to 75–88 kilometres per hour (20.8–24.4 metres per second). According to the Beaufort scale, which uses ten-minute average wind speeds, the same threshold applies for classifying a storm. A severe storm corresponds to force 10, while a very severe storm reaches force 11. Force 12 indicates hurricane conditions, which are exceptionally rare in the Netherlands. A register of all storms reaching force 10 or higher has been maintained since 1910.

The highest wind speeds are generally observed along the Dutch coast, where the wind is only minimally obstructed by terrain and friction. Coastal areas therefore experience storms more frequently than the interior of the country. For instance, in Vlissingen storms occur several times per year, while in De Bilt, located centrally, force 9 winds are recorded only once in approximately seventy years. Severe storms of force 10 are extremely uncommon over land.

Storm depressions usually originate from large contrasts in atmospheric temperature, which is why the most intense storms occur during the colder half of the year, between October and March. In the northern hemisphere, cold air masses descend from the north while milder conditions persist in the south, producing sharp temperature gradients. These gradients drive the development of a strong jet stream at around 10 kilometres altitude, which steers successive depressions towards north-western Europe. When atmospheric conditions are unstable, storms may follow each other in quick succession.

Storm season

The storm season officially begins in September, though the first storm generally occurs in November. Storms in the summer half of the year (April to September) are referred to as summer storms. These are relatively rare compared to winter storms (October to March), and tend to be less intense and of shorter duration due to smaller temperature contrasts. Nevertheless, summer storms often result in significant disruption. Their rapid development can catch road traffic and maritime activities unprepared, and full foliage on trees makes them particularly vulnerable to wind damage, especially during periods of heavy rainfall.

Warning codes

The Royal Netherlands Meteorological Institute (KNMI) can issue warnings for severe gusts of wind based on meteorological guidelines and expected impact. For all warnings, the anticipated impact is the leading factor. The extent to which the weather poses a risk determines whether the KNMI issues a yellow, orange, or red warning.

  • Code Yellow: From 75 kilometres per hour (km/h) with an exception during the winter half-year, from 90 km/h at the coast.
  • Code Orange and Code Red: From 100 km/h with an exception during the winter half-year, from 120 km/h at the coast.

Since 2019, storms for which the KNMI issues an orange or red warning for wind gusts are assigned a name. With the use of storm names they aim to raise awareness of dangerous weather. In exceptional cases, storms may also be named under a yellow warning. Separate storm warnings continue to be issued for maritime traffic and for coastal and North Sea districts.

Downbursts

Downbursts (Valwind in Dutch) are powerful downward air currents that occur during intense thunderstorms or heavy rain showers. When a large mass of cold air descends rapidly from a storm cloud and spreads out upon reaching the ground, it can cause significant local damage. Unlike tornadoes, downbursts do not involve rotating columns of air. However, they can uproot trees, damage roofs, and pose serious risks to traffic and water sports. In the Netherlands, downbursts occasionally occur, particularly in summer months during active storm systems. Though typically short-lived, their sudden and intense nature makes them particularly hazardous.

Blizzards (Snowstorm)

A blizzard or snowstorm is defined as snowfall or drifting snow accompanied by wind speeds of force 8 or higher on the Beaufort scale. A snowstorm occurring with sub-zero temperatures and wind force 8 or 9 is considered exceptional. During the twentieth century, such events occurred on average once every five years, although their distribution over time was highly irregular. In some cases, more than twenty years would pass before the next snowstorm, while in particularly severe winters, multiple snowstorms could occur within a single season.

The most recent snowstorm took place on 7 February 2021, during which the KNMI assigned the storm the name Darcy due to the exceptional weather conditions. A previous snowstorm occurred on 9 January 2010 in the northern part of the country. The last severe snowstorm of the twentieth century dates back to 1985, when snow fell on 8 and 9 January accompanied by storm-force winds.

Dust storm and Sandstorm

The Netherlands is occasionally affected by fine dust and sand originating from the Sahara. This phenomenon occurs when strong southerly air currents transport the dust thousands of kilometres northward. The particles are subsequently deposited on the ground via rainfall, often visible as a reddish-brown residue on cars and garden furniture. Since 1900, this occurrence has been observed on a large scale in the Netherlands at least fifteen times.

Localised sandstorms or drifting sand can also occur within the Netherlands, particularly during dry weather conditions, strong winds, and over exposed agricultural land. While these events are not comparable to the vast sandstorms found in desert regions, they can temporarily reduce visibility and cause irritation to the eyes and respiratory system.

In addition, small whirlwinds that lift sand, leaves, or lightweight objects occasionally form. These are typically harmless and short-lived.