Service
Japan Meteorological Agency (JMA) Bosai weather data: office-level short-term and weekly forecasts with JMA's forecast narrative, the official forecast area code hierarchy, current AMeDAS observations from the station nearest a point, and the analysis and forecasts of every tropical cyclone JMA is tracking, served from the keyless public JSON endpoints at www.jma.go.jp.
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Selecting a row opens the reference for that API.
| Method | API | Path | Summary |
|---|---|---|---|
| POST | /v1/jma-weather/active-typhoons | Returns every tropical cyclone JMA is currently tracking in the western North Pacific, each with its current analysis and JMA's forecasts, from bosai/typhoon/data/targetTc.json and each cyclone's specifications.json. Every state carries its kind (analysis, one-hour estimate, or forecast), lead hours, valid time, grade (typhoon, severe tropical storm, tropical storm, tropical depression, extratropical cyclone), JMA's size and intensity classes, center latitude/longitude, movement direction and speed, central pressure in hPa, maximum sustained wind and gust in m/s, and wind areas as radii in km per side of the center: the storm area (25 m/s or more) and gale area (15 m/s or more) for the analysis and estimate, and the probability circle and storm warning area for forecasts. Use when you need to know whether a typhoon is active, where it is, how strong it is, and where JMA forecasts it to go. Takes no input. An empty typhoons list is JMA's normal answer when no cyclone is active. Do NOT use for local weather forecasts — use jma-weather:forecast-by-area. Names and location_text are JMA's Japanese text, verbatim; values JMA does not publish for a state (no size class on a forecast, no maximum wind for a tropical depression) are null. | |
| POST | /v1/jma-weather/area-code-map | Returns the official JMA area hierarchy from bosai/common/const/area.json: centers (regional blocks), offices (prefecture-level forecast offices; the jma-weather:forecast-by-area input vocabulary), class10 primary subdivisions, class15 grouped-municipality areas, and class20 municipalities with kana readings. A few offices have no forecast file of their own: as of 2026-07-20, 014030 Tokachi and 460040 Amami return NOT_FOUND because their forecasts are published under sibling offices 014100 and 460100. Use when you need to resolve a place to a forecast area code or walk parent/child relations of the official hierarchy. Do NOT use for weather values — use jma-weather:forecast-by-area instead. This is a static reference map maintained by JMA that changes only when administrative areas change. Returns centers, offices, class10_areas, class15_areas, and class20_areas. | |
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| /v1/jma-weather/current-observation |
| Fetches the latest JMA AMeDAS observation from the station nearest to a WGS84 latitude/longitude. It reads amedas/data/latest_time.txt, the 10-minute map snapshot it names, and JMA's official station table, selects the nearest station that published in that snapshot, and returns that one station's identity, coordinates, distance from the requested point, observation time, and the readings it carries (temperature, humidity, station and sea-level pressure, visibility, wind speed and direction, 10-minute to 24-hour precipitation, sunshine duration). Use when you need what the weather is right now near a place in Japan. Do NOT use for forecasts — use jma-weather:forecast-by-area instead; forecast office area codes are a different vocabulary and do not identify an AMeDAS station. Readings JMA flags as anything other than normal or quasi-normal are returned as null, never as the doubtful number. Check distance_meters: the nearest station can be far from a point outside Japan's station network. Returns station_code, station_name, station_name_english, latitude, longitude, elevation_meters, distance_meters, observation_time, and the station's readings. |
| POST | /v1/jma-weather/forecast-by-area | Fetches the official JMA forecast for one forecast office area code (e.g. 130000 for Tokyo) and returns both report blocks JMA publishes: a short-term report (~3 days of weather codes, Japanese weather/wind/wave text, precipitation probabilities, and forecast daily minimum/maximum temperatures on time-labeled slots) and a weekly report (7-day weather codes, precipitation probabilities, forecast reliability classes, min/max temperature ranges, and climatological normals). Use when you need the authoritative Japanese government forecast for a prefecture-level area. Do NOT use for resolving a city or place name to an area code or for browsing the area hierarchy — use jma-weather:area-code-map instead. Area codes are JMA office codes from jma-weather:area-code-map, never city names or coordinates. Unknown area codes return a structured NOT_FOUND error (upstream HTTP 404). Weather codes are pattern-validated 3-digit strings from JMA's open-ended code table; the Japanese text fields carry the human-readable forecast. Returns area_code, short_term, and weekly. |
| POST | /v1/jma-weather/forecast-overview-by-area | Returns JMA's Japanese forecast narrative (天気概況) for one forecast office area code (e.g. 130000 for Tokyo): the publishing office, the report time, the target area name, the headline, and the narrative prose, all verbatim from bosai/forecast/data/overview_forecast/{area_code}.json. Use when you need JMA's own explanation of the weather situation behind the forecast — fronts, pressure systems, and what to expect — in Japanese. Do NOT use for structured forecast values (weather codes, precipitation probabilities, temperatures) — use jma-weather:forecast-by-area instead. Area codes are JMA office codes from jma-weather:area-code-map; the same two offices without a forecast file (014030 Tokachi, 460040 Amami) have no overview either and return NOT_FOUND. The Japanese text is never translated; headline_text is an empty string outside special-weather situations. Returns area_code, publishing_office, report_datetime, target_area, headline_text, and narrative_text. |
