KNMI Forecast API

Weather forecasts from the Royal Netherlands Meteorological Institute

Location and Time

Location:

Latitude

Longitude

Timezone

API Mode:

Time:

Forecast days

Past days

Forecast provides the latest, continuously updated weather forecast. By default, we provide forecasts for 3 days, but you can access forecasts for up to 15 days. Use Past Days to include recently archived forecasts.

For older archived forecasts, switch to mode.

You can also check out our Historical Weather API with data going back to 1940.

Hourly Weather Variables

Temperature (2 m)

Relative Humidity (2 m)

Dewpoint (2 m)

Apparent Temperature

Precipitation (rain + snow)

Rain

Snowfall

Snow Depth Water Equivalent

Weather code

Sea Level Pressure

Surface Pressure

Cloud Cover Total

Cloud Cover Low

Cloud Cover Mid

Cloud Cover High

Visibility

Reference Evapotranspiration (ET₀)

Vapour Pressure Deficit

Wind Speed (10 m)

Wind Speed (50 m)

Wind Speed (100 m)

Wind Speed (200 m)

Wind Speed (300 m)

Wind Direction (10 m)

Wind Direction (50 m)

Wind Direction (100 m)

Wind Direction (200 m)

Wind Direction (300 m)

Wind Gusts (10 m)

Surface Temperature

Temperature (5 m)

Temperature (100 m)

Temperature (200 m)

Temperature (300 m)

Daily Weather Variables

Weather code

Maximum Temperature (2 m)

Minimum Temperature (2 m)

Maximum Apparent Temperature (2 m)

Minimum Apparent Temperature (2 m)

Sunrise

Sunset

Daylight Duration

Sunshine Duration

UV Index

UV Index Clear Sky

Precipitation Sum

Rain Sum

Showers Sum

Snowfall Sum

Precipitation Hours

Maximum Wind Speed (10 m)

Maximum Wind Gusts (10 m)

Dominant Wind Direction (10 m)

Shortwave Radiation Sum

Reference Evapotranspiration (ET₀)

Settings

Temperature Unit

Wind Speed Unit

Precipitation Unit

Timeformat

Usage licence:

API Response

Preview:

Download XLSX Download CSV

API URL (Open in new tab or copy this URL into your application)

Data Sources

KNMI provides weather forecasts from the HARMONIE AROME model with ECMWF IFS initialization. This is a collaboration of multiple European national weather services under the name "United Weather Centres-West" (UWC-West). Two model configuration one for Europe (5.5 km resolution) and an inset for the Netherlands (2 km resolution) are available. All data is updated hourly and provides forecast for up to 2.5 days. After 2.5 days, Open-Meteo combines forecasts with the ECMWF IFS HRES 9 km model to provide up to 15 days of forecast.

Weather Model	Region	Spatial Resolution	Temporal Resolution	Forecast Length	Update frequency
KNMI HARMONIE AROME Netherlands	Netherlands, Belgium	2 km	1-hourly	2.5 days	Every hour
KNMI HARMONIE AROME Europe	Central & Northern Europe up to Iceland	5.5 km	1-hourly	2.5 days	Every hour

KNMI HARMONIE AROME Europe Model Area. Source: Open-Meteo.

KNMI HARMONIE AROME Netherlands Model Area. Source: Open-Meteo.

Native Model Variables

HARMONIE AROME directly predicts the fields listed below. Open-Meteo retains these fields or uses them to calculate more convenient API variables. The model provides wind as U and V components and only global solar radiation.

Native KNMI field	Level	Use in the Open-Meteo API
Temperature	2 m, 50/100/200/300 m, surface, pressure levels	temperature_2m and upper-level temperature
Relative humidity	2 m, pressure levels	Relative humidity, dew point and pressure-level cloud cover
U and V wind components	10 m to 300 m, pressure levels	Wind speed and direction
Wind gust components	10 m	wind_gusts_10m
Mean sea-level pressure	Mean sea level	pressure_msl and derived surface pressure
Precipitation, rain and snowfall water equivalent	Surface	precipitation, rain, snowfall, showers
Global solar radiation	Surface	Global, direct, diffuse radiation, DNI and GTI
Cloud cover total, low, mid and high	Surface	cloud_cover and the individual layers
Visibility and snow depth	Surface	visibility, snow_depth_water_equivalent
Geopotential	Pressure levels (Europe)	geopotential_height

Pressure-level data and wind above 10 m are only available in the Europe 5.5 km model.

Derived Variables

HARMONIE AROME natively provides temperature, relative humidity, cloud cover, precipitation, visibility and global solar radiation. Several convenient API variables are not direct model output — Open-Meteo derives them from the native fields for every forecast step.

Derived Variable	How it is derived?
Wind speed and direction	Calculated from the native U and V wind components. On the rotated Europe grid the direction is corrected for the projection; without this correction it would be off by up to 15°.
Direct and diffuse solar radiation	Only global horizontal irradiance GHI is native. Diffuse radiation is separated using the Razo, Müller Witwer model; direct radiation is the remainder. DNI, GTI and instant values follow from solar geometry.
Weather code	Computed from cloud cover, precipitation, snowfall, wind gusts and visibility. KNMI provides no CAPE, so thunderstorm codes are not produced.
Snowfall and showers	Snowfall converts the native snowfall water equivalent with 0.7 cm per mm. Showers are precipitation minus the native rain and snowfall water equivalent.
Dew point, vapour pressure deficit and wet bulb temperature	Calculated from native 2 m temperature and relative humidity.
Surface pressure	Calculated from mean sea-level pressure, 2 m temperature and terrain elevation.
Sunshine duration	Seconds per hour with derived direct normal irradiance above the WMO threshold of 120 W/m².
Apparent temperature and reference evapotranspiration ET₀	Combine temperature, humidity, wind speed and solar radiation. ET₀ follows the FAO-56 Penman-Monteith equation.
Pressure-level cloud cover and dew point	Estimated from pressure-level relative humidity and temperature (Europe model only).

Sunrise, sunset, daylight duration and the day-or-night flag are astronomical calculations. Daily values are aggregated from hourly data.

API Documentation

For a detailed list of all available weather variables please refer to the general Weather Forecast API. Only notable remarks are listed below

Solar Radiation: KNMI supplies only global solar radiation data and does not offer direct or diffuse solar radiation. Open-Meteo applies the separation model from Razo, Müller Witwer to calculate direct radiation from shortwave solar radiation.
Wind Direction Correction: Wind direction has been calculated from U/V wind component vectors. Special care has been taken to correct for the Rotated Lat Long projection. Without this correction, wind directions have an error of up to 15°.
Wind on 50, 100, 200, 300m: Wind forecasts for higher altitudes are only available for the Netherlands area.
Pressure Level Data: Forecasts on pressure level are only available for the European model.