FAQ

WOW-NL is the Dutch network of the Weather Observations Website: a crowdsourced platform on which individuals, schools and organisations share current weather observations. These observations complement the official KNMI observation network and provide more local detail, for example in towns and villages. For more than ten years, around a thousand weather enthusiasts in the Netherlands have been sharing observations from their personal weather stations via WOW-NL.

Data from personal stations is not the same as validated measurements from official KNMI stations. Participants are themselves responsible for the placement and maintenance of their weather station and for the quality and completeness of the data they supply.

Together with the measurements from the official KNMI weather stations, these observations give an increasingly detailed picture of the weather in the Netherlands. Think of more insight into trends in extreme weather, knowledge of the urban climate and more detailed advice on the impact of the weather.

To describe, understand and forecast the weather well, observations are needed from very different environments: from countryside to city, from dunes and forests to polders and high sandy soils. Personal weather stations complement the official network with many additional local observations.

The data from WOW-NL is used for research and to show local differences more clearly, for example during extreme weather and in research into heat in urban areas. Since 2024, WOW measurements have also been used in maps in the KNMI app. In these maps, WOW measurements from citizens are combined with data from official KNMI weather stations.

Yes. Participation is free and open to anyone with an automatic weather station that can send data over the internet. The brand or price range is not decisive; whether the weather station can work with WOW-NL, careful placement and continuity of the measurements are more important.

• An automatic weather station with outdoor sensors.
• An internet connection and a way to upload data: directly from the weather station, via an app, or via software on a computer, for example a Raspberry Pi.
• An account and a registered measurement location on the WOW platform.
• The station details with which the upload is recognised.

If the upload runs via software on a computer, that computer must be active 24/7 whenever you want to send data. For permanent use, a separate device may be more suitable, such as the separate Ecowitt device, WeatherLink Live, Meteobridge or an energy-efficient mini computer, for example a Raspberry Pi.

WOW does not prescribe a brand. A suitable station is called “WOW-ready”. Before buying, check whether the station can use a custom server, custom upload or DIY upload and supports the WOW, Weather Underground or Ecowitt protocol. Connecting via software such as Meteobridge, CumulusMX, WeeWX or Weather Display may also be possible.

More information can be found under “Join”.

KNMI, together with the Belgian RMI, shares the renewed WOW-BE platform of the RMI. You can easily sign up with an existing account (via social authentication) under “Login”. Log in and choose Register a station. After registration you will receive a long and a short station ID; you chose the authentication key yourself during registration.

Store your station ID and key safely. An authentication key does not belong in a public message, screenshot or online configuration file.

In the app or web interface, choose a custom server. When using the Weather Underground protocol, these are the settings published by the WOW-BE platform:

Do not enter http:// twice if the app already shows it before the server field. For devices with a server choice, select Customized, not the old option WeatherObservationsWebsite.

Yes, if your station or a separate device supports it. Use host wow.meteo.be, path /api/v2/send? and port 80. With this protocol, the platform identifies the station by its MAC address*; so register the correct MAC address for your station. A separate ID and key are not entered with this upload method.

If this does not work, try the Weather Underground configuration. Note that a MAC address consists of twelve hexadecimal characters and is easily copied incorrectly.

* MAC address: a unique sequence of letters and numbers by which a device is recognised within a network. You can usually find the MAC address of the weather station or the separate device in the accompanying app, on a sticker or in the network settings.

An interval of one minute is the current recommendation of the WOW-BE platform. A higher measurement frequency in the station does not always mean that every individual measurement becomes visible: the platform may combine several measurements into one value or display the data with its own refresh interval.

Register your station again on the WOW-BE platform. You will receive new identification details. In your upload software, change or add the new endpoint http://wow.meteo.be/api/v2/send? and use your new station ID and authentication key.

The old Site ID and six-digit AWS PIN are not your new login details. Leave a still-working British upload in place in parallel for the time being if your software supports multiple services.

A sensor does not only measure the weather, but also the influence of its immediate surroundings. A warm wall can raise the temperature, trees can intercept wind and rain, and paving can store heat during the day. A simple sensor in a good location can therefore deliver more usable data than an expensive sensor in an unsuitable location.

Can you not meet all the guidelines? Then state in the station description how and where the sensors are placed. Measurements from a city garden or a balcony can also be valuable, provided their context is known.

Place it over a natural surface, for example grass, in a white, all-round ventilated radiation shield that keeps out direct sunlight and precipitation, and as far as possible from walls, roofs, paving, exhausts and other heat sources. Direct sunlight often causes a clear positive measurement error; placing it “in the shade” alone is not always enough, because still air and a warm wall also affect the measurement. Clean the temperature sensor and the radiation shield when visibly dirty.

A humidity sensor may deviate by a few percent. In dense fog and a temperature above zero, a value close to saturation — roughly 95–100% — is a useful practical check.

Level the rain gauge, with a free inflow and not close to trees, walls or roof edges. Regularly clear the funnel and tipping bucket of leaves, insects and dirt.

An anemometer needs as much free airflow as possible on all sides. Obstacles cause shelter and turbulence; as a result, wind speed and wind direction at a sheltered location are often less representative. Note the mounting height and relevant obstacles in the station description. With an all-in-one sensor array a compromise is unavoidable: document it.

Place a radiation sensor horizontally and level in a location with as clear a view of the sky as possible. Make sure buildings, trees, antennas and other parts of the weather station do not cast a shadow on the sensor at any time of the day. Also keep the sensor away from strongly reflective surfaces, such as light-coloured walls or metal roofs.

Regularly check whether the sensor is still level and carefully clean the sensor surface in case of dust, bird droppings, snow or other contamination. Follow the manufacturer’s cleaning instructions and avoid scratching the diffuser or sensor cover.

An air pressure sensor may be placed indoors, because air pressure indoors and outdoors is almost the same. Place the sensor in a dry location with as constant a temperature as possible. Avoid direct sunlight and places close to a heater, air conditioner, open window or exterior door.

Make sure the sensor stays in contact with the ambient air and therefore do not seal it airtight. Note the height of the sensor above sea level in the station details; this height is needed to convert the air pressure to sea level correctly.

First check which pressure field your software sends. Absolute air pressure is the pressure at the actual height of the sensor; relative air pressure is converted to sea level and is therefore suitable for comparing locations. Send these values to the correct field and do not apply a height correction both in the station and in the upload software.

An almost constant deviation compared with neighbouring stations often points to an incorrect height, the wrong pressure type or a double correction.

1. Check whether the station itself shows recent values and has internet access.
2. Carefully compare the server address, upload path and port number you entered with the prescribed settings. One missing or wrong digit, letter or punctuation mark can block the upload. Pay particular attention to the slash (/) and the question mark in /api/v2/send?.
3. Check the short station ID and the authentication key, or for Ecowitt the registered MAC address.
4. Check whether the custom upload is enabled and the interval is not set to “off”.
5. If necessary, restart only the upload function, the separate device or the software and wait a few upload intervals.
6. Look at a log or upload status. Messages such as 401 or 403 usually point to identification; 404 often to an incorrect path.

The map may refresh later than the upload. Registering again several times does not help then and can actually cause confusion through different station IDs.

A difference is not automatically a defect. Distance, height, cloud cover, ground, buildings and shelter can cause real local differences. Preferably compare over several days with different types of weather and with more than one neighbouring station.

• Temperature too high mainly in sunshine: think of radiation influence or too little ventilation.
• Wind almost always too low: think of obstacles or a low mounting height.
• Rain structurally too low: check shelter, contamination and levelling.
• Pressure almost constantly offset: check height and absolute/relative.

Only calibrate after placement, configuration and maintenance have been checked. Correcting on the basis of a single snapshot can introduce a new error.

Short spikes can be caused by a sensor connection dropping out, a flat battery, a restart, radio interference, dirt in the rain gauge or a software error. Missing values often occur when wifi, internet, the separate device or the upload computer is temporarily down.

Check the times in the local log and compare different variables: if they all drop out at the same time, the cause is probably in the connection or upload. If only one variable is disturbed, investigate that sensor first.