JMA API

5-km high resolution forecasts for Japan, Korea, parts of China and Russia

Location and Time

Hourly Weather Variables

Daily Weather Variables

Current Weather

Note: Current conditions are based on 15-minutely weather model data. Every weather variable available in hourly data, is available as current condition as well.

Settings

API Response

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

Data Source

This API uses global and local weather models from the Japan Meteorological Agency JMA. Due to data license restrictions only a limited version of data is available. A list of official JMA data is available on the JMA website. For GSM, values are interpolated from 6-hourly to 1-hourly values.

You can find the update timings in the model updates documentation.
Weather ModelRegionSpatial ResolutionTemporal ResolutionForecast LengthUpdate frequency
GSMGlobal0.5° (~55 km)6-Hourly11 daysEvery 6 hours
MSMJapan, Korea0.05° (~5 km)Hourly4 daysEvery 3 hours
JMA models like RSM are not available.
...
JMA MSM model area. Source: Open-Meteo.

API Documentation

The API endpoint /v1/jma accepts a geographical coordinate, a list of weather variables and responds with a JSON hourly weather forecast for 4 days. Time always starts at 0:00 today and contains 168 hours. All URL parameters are listed below:

You can find the update timings in the model updates documentation.
ParameterFormatRequiredDefaultDescription
latitude, longitudeFloating pointYesGeographical WGS84 coordinates of the location. Multiple coordinates can be comma separated. E.g. &latitude=52.52,48.85&longitude=13.41,2.35. To return data for multiple locations the JSON output changes to a list of structures. CSV and XLSX formats add a column location_id.
elevationFloating pointNoThe elevation used for statistical downscaling. Per default, a 90 meter digital elevation model is used. You can manually set the elevation to correctly match mountain peaks. If &elevation=nan is specified, downscaling will be disabled and the API uses the average grid-cell height. For multiple locations, elevation can also be comma separated.
hourlyString arrayNoA list of weather variables which should be returned. Values can be comma separated, or multiple &hourly= parameter in the URL can be used.
dailyString arrayNoA list of daily weather variable aggregations which should be returned. Values can be comma separated, or multiple &daily= parameter in the URL can be used. If daily weather variables are specified, parameter timezone is required.
currentString arrayNoA list of weather variables to get current conditions.
temperature_unitStringNocelsiusIf fahrenheit is set, all temperature values are converted to Fahrenheit.
wind_speed_unitStringNokmhOther wind speed speed units: ms, mph and kn
precipitation_unitStringNommOther precipitation amount units: inch
timeformatStringNoiso8601If format unixtime is selected, all time values are returned in UNIX epoch time in seconds. Please note that all timestamp are in GMT+0! For daily values with unix timestamps, please apply utc_offset_seconds again to get the correct date.
timezoneStringNoGMTIf timezone is set, all timestamps are returned as local-time and data is returned starting at 00:00 local-time. Any time zone name from the time zone database is supported. If auto is set as a time zone, the coordinates will be automatically resolved to the local time zone. For multiple coordinates, a comma separated list of timezones can be specified.
past_daysIntegerNo0If past_days is set, past weather data can be returned.
forecast_daysInteger (0-11)No7Per default, 7 days are returned. Up to 11 days of forecast are possible.
forecast_hours
past_hours
Integer (>0)NoSimilar to forecast_days, the number of timesteps of hourly data can controlled. Instead of using the current day as a reference, the current hour is used.
start_date
end_date
String (yyyy-mm-dd)NoThe time interval to get weather data. A day must be specified as an ISO8601 date (e.g. 2022-06-30).
start_hour
end_hour
String (yyyy-mm-ddThh:mm)NoThe time interval to get weather data for hourly data. Time must be specified as an ISO8601 date (e.g. 2022-06-30T12:00).
cell_selectionStringNolandSet a preference how grid-cells are selected. The default land finds a suitable grid-cell on land with similar elevation to the requested coordinates using a 90-meter digital elevation model. sea prefers grid-cells on sea. nearest selects the nearest possible grid-cell.
apikeyStringNoOnly required to commercial use to access reserved API resources for customers. The server URL requires the prefix customer-. See pricing for more information.

Additional optional URL parameters will be added. For API stability, no required parameters will be added in the future!

Hourly Parameter Definition

The parameter &hourly= accepts the following values. Most weather variables are given as an instantaneous value for the indicated hour. Some variables like precipitation are calculated from the preceding hour as an average or sum.

VariableValid timeUnitDescription
temperature_2mInstant°C (°F)Air temperature at 2 meters above ground
relative_humidity_2mInstant%Relative humidity at 2 meters above ground
dew_point_2mInstant°C (°F)Dew point temperature at 2 meters above ground
apparent_temperatureInstant°C (°F)Apparent temperature is the perceived feels-like temperature combining wind chill factor, relative humidity and solar radiation
pressure_msl
surface_pressure
InstanthPaAtmospheric air pressure reduced to mean sea level (msl) or pressure at surface. Typically pressure on mean sea level is used in meteorology. Surface pressure gets lower with increasing elevation.
cloud_coverInstant%Total cloud cover as an area fraction
cloud_cover_lowInstant%Low level clouds and fog up to 3 km altitude
cloud_cover_midInstant%Mid level clouds from 3 to 8 km altitude
cloud_cover_highInstant%High level clouds from 8 km altitude
wind_speed_10mInstantkm/h (mph, m/s, knots)Wind speed at 10 meters above ground. Wind speed on 10 meters is the standard level.
wind_direction_10mInstant°Wind direction at 10 meters above ground
shortwave_radiationPreceding hour meanW/m²Shortwave solar radiation as average of the preceding hour. This is equal to the total global horizontal irradiation
direct_radiation
direct_normal_irradiance
Preceding hour meanW/m²Direct solar radiation as average of the preceding hour on the horizontal plane and the normal plane (perpendicular to the sun). JMA does not offers diffuse and direct radiation directly. It is approximated based on Razo, Müller Witwer
diffuse_radiationPreceding hour meanW/m²Diffuse solar radiation as average of the preceding hour. MA does not offers diffuse and direct radiation directly. It is approximated based on Razo, Müller Witwer
global_tilted_irradiancePreceding hour meanW/m²Total radiation received on a tilted pane as average of the preceding hour. The calculation is assuming a fixed albedo of 20% and in isotropic sky. Please specify tilt and azimuth parameter. Tilt ranges from 0° to 90° and is typically around 45°. Azimuth should be close to 0° (0° south, -90° east, 90° west). If azimuth is set to "nan", the calculation assumes a horizontal tracker. If tilt is set to "nan", it is assumed that the panel has a vertical tracker. If both are set to "nan", a bi-axial tracker is assumed.
sunshine_durationPreceding hour sumSecondsNumber of seconds of sunshine of the preceding hour per hour calculated by direct normalized irradiance exceeding 120 W/m², following the WMO definition.
vapour_pressure_deficitInstantkPaVapor Pressure Deificit (VPD) in kilopascal (kPa). For high VPD (>1.6), water transpiration of plants increases. For low VPD (<0.4), transpiration decreases
et0_fao_evapotranspirationPreceding hour summm (inch)ET₀ Reference Evapotranspiration of a well watered grass field. Based on FAO-56 Penman-Monteith equations ET₀ is calculated from temperature, wind speed, humidity and solar radiation. Unlimited soil water is assumed. ET₀ is commonly used to estimate the required irrigation for plants.
weather_codeInstantWMO codeWeather condition as a numeric code. Follow WMO weather interpretation codes. See table below for details. Weather code is calculated from cloud cover analysis, precipitation and snowfall. As JMA has barely no information about atmospheric stability, estimation about thunderstorms is not possible.
precipitationPreceding hour summm (inch)Total precipitation (rain, showers, snow) sum of the preceding hour
snowfallPreceding hour sumcm (inch)Snowfall amount of the preceding hour in centimeters. For the water equivalent in millimeter, divide by 7. E.g. 7 cm snow = 10 mm precipitation water equivalent. Snowfall amount is not provided by JMA directly, instead it is approximated based on total precipitation and temperature

Pressure Level Variables

Pressure level variables do not have fixed altitudes. Altitude varies with atmospheric pressure. 1000 hPa is roughly between 60 and 160 meters above sea level. Estimated altitudes are given below. Altitudes are in meters above sea level (not above ground). For precise altitudes, geopotential_height can be used.

Level (hPa)1000925850700500400300250200150100
Altitude110 m800 m1500 m3 km5.6 km7.2 km9.2 km10.4 km11.8 km13.5 km15.8 km

All pressure level have valid times of the indicated hour (instant).

VariableUnitDescription
temperature_1000hPa
temperature_975hPa, ...
°C (°F)Air temperature at the specified pressure level. Air temperatures decrease linearly with pressure.
relative_humidity_1000hPa
relative_humidity_975hPa, ...
%Relative humidity at the specified pressure level.
dew_point_1000hPa
dew_point_975hPa, ...
°C (°F)Dew point temperature at the specified pressure level.
cloud_cover_1000hPa
cloud_cover_975hPa, ...
%Cloud cover at the specified pressure level. JMA models do not inlude parameterised cloud cover directly. It is approximated based on relative humidity using Sundqvist et al. (1989). It may not match perfectly with low, mid and high cloud cover variables.
wind_speed_1000hPa
wind_speed_975hPa, ...
km/h (mph, m/s, knots)Wind speed at the specified pressure level.
wind_direction_1000hPa
wind_direction_975hPa, ...
°Wind direction at the specified pressure level.
geopotential_height_1000hPa
geopotential_height_975hPa, ...
meterGeopotential height at the specified pressure level. This can be used to get the correct altitude in meter above sea level of each pressure level. Be carefull not to mistake it with altitude above ground.

Daily Parameter Definition

Aggregations are a simple 24 hour aggregation from hourly values. The parameter &daily= accepts the following values:

VariableUnitDescription
weather_codeWMO codeThe most severe weather condition on a given day
temperature_2m_max
temperature_2m_min
°C (°F)Maximum and minimum daily air temperature at 2 meters above ground
apparent_temperature_max
apparent_temperature_min
°C (°F)Maximum and minimum daily apparent temperature
precipitation_summmSum of daily precipitation (including rain, showers and snowfall)
precipitation_hourshoursThe number of hours with rain
snowfall_sumcmSum of daily snowfall
sunrise
sunset
iso8601Sun rise and set times
sunshine_durationsecondsThe number of seconds of sunshine per day is determined by calculating direct normalized irradiance exceeding 120 W/m², following the WMO definition. Sunshine duration will consistently be less than daylight duration due to dawn and dusk.
daylight_durationsecondsNumber of seconds of daylight per day
wind_direction_10m_dominant°Dominant wind direction
shortwave_radiation_sumMJ/m²The sum of solar radiation on a given day in Megajoules
et0_fao_evapotranspirationmmDaily sum of ET₀ Reference Evapotranspiration of a well watered grass field

JSON Return Object

On success a JSON object will be returned.

      

  "latitude": 52.52,
  "longitude": 13.419,
  "elevation": 44.812,
  "generationtime_ms": 2.2119,
  "utc_offset_seconds": 0,
  "timezone": "Europe/Berlin",
  "timezone_abbreviation": "CEST",
  "hourly": {
    "time": ["2022-07-01T00:00", "2022-07-01T01:00", "2022-07-01T02:00", ...],
    "temperature_2m": [13, 12.7, 12.7, 12.5, 12.5, 12.8, 13, 12.9, 13.3, ...]
  },
  "hourly_units": {
    "temperature_2m": "°C"
  }

      
    
ParameterFormatDescription
latitude, longitudeFloating pointWGS84 of the center of the weather grid-cell which was used to generate this forecast. This coordinate might be a few kilometers away from the requested coordinate.
elevationFloating pointThe elevation from a 90 meter digital elevation model. This effects which grid-cell is selected (see parameter cell_selection). Statistical downscaling is used to adapt weather conditions for this elevation. This elevation can also be controlled with the query parameter elevation. If &elevation=nan is specified, all downscaling is disabled and the averge grid-cell elevation is used.
generationtime_msFloating pointGeneration time of the weather forecast in milliseconds. This is mainly used for performance monitoring and improvements.
utc_offset_secondsIntegerApplied timezone offset from the &timezone= parameter.
timezone
timezone_abbreviation
StringTimezone identifier (e.g. Europe/Berlin) and abbreviation (e.g. CEST)
hourlyObjectFor each selected weather variable, data will be returned as a floating point array. Additionally a time array will be returned with ISO8601 timestamps.
hourly_unitsObjectFor each selected weather variable, the unit will be listed here.
dailyObjectFor each selected daily weather variable, data will be returned as a floating point array. Additionally a time array will be returned with ISO8601 timestamps.
daily_unitsObjectFor each selected daily weather variable, the unit will be listed here.

Errors

In case an error occurs, for example a URL parameter is not correctly specified, a JSON error object is returned with a HTTP 400 status code.

      

  "error": true,
  "reason": "Cannot initialize WeatherVariable from invalid String value tempeture_2m for key hourly"