Japan Weather Forecast & Warnings (JMA official data)

Turn the Japan Meteorological Agency (JMA / 気象庁) open weather feeds into clean, English-labelled records. This Actor reads JMA's own public bosai JSON — the same data that powers the official jma.go.jp site — and restructures it: weather codes and warning codes resolved to English, wind directions parsed to cardinals, precipitation probability and representative temperatures attached per day.

No API key. No login. Public government open data.

Forecasts, not observations. For what the weather is right now — live temperature, rain, wind, sunshine and humidity from JMA's ~1,300 AMeDAS stations — see the sibling Actor Japan AMeDAS Weather Observations (JMA). This Actor covers what the weather will be.

Quick start — verified input

Copy, paste, run. This exact input is verified on the platform (SUCCEEDED, items > 0):

{
  "mode": "forecast",
  "prefecture": "Tokyo",
  "maxItems": 100
}

Running with no input at all also works (it uses the same defaults). prefecture is a dropdown of the 47 English prefecture names; via the API you may also pass the Japanese name ("東京都"), the JIS code ("13"), or common romanisations ("osaka-fu", "Ōsaka", "Tokyo-to").

What you get

Pick a prefecture (Tokyo, 13, or 東京都) and a mode:

• forecast — one record per forecast subdivision, with a merged daily forecasts[] array covering the 3-day near-term forecast (weather, wind, wave, precipitation probability) plus the extended weekly forecast (weather, precipitation probability, reliability grade, min/max temperature).
• warning — one record per forecast area listing the current 警報・注意報 (warnings / advisories), each with the JMA code resolved to an English name and a severity class (emergency / warning / advisory), plus hasActiveWarning.
• overview — the plain-language regional outlook (概況) text, passed through verbatim in Japanese with attribution.

Example output (forecast, one day)

{
  "mode": "forecast",
  "prefectureCode": "13",
  "areaCode": "130010",
  "areaNameEn": "Tokyo Region",
  "areaNameJa": "東京地方",
  "reportDatetime": "2026-08-25T17:00:00+09:00",
  "publishingOffice": "気象庁",
  "forecasts": [
    {
      "date": "2026-08-26",
      "weatherCode": "111",
      "weatherEn": "Clear, later cloudy",
      "weatherJa": "晴後曇",
      "windDirection": "South",
      "waveJa": "0.5メートル",
      "precipProbability": 30,
      "tempMin": 26,
      "tempMax": 35,
      "reliability": null,
      "timeframe": "near_term"
    }
  ],
  "source": "気象庁 bosai JSON ... / Japan Meteorological Agency (JMA) open weather data",
  "sourceUrl": "https://www.jma.go.jp/bosai/",
  "license": "出典：気象庁ホームページ（https://www.jma.go.jp/）。...",
  "retrievedAt": "2026-08-26T12:00:00.000Z"
}

Every record carries the four attribution fields (source, sourceUrl, license, retrievedAt).

Input

Field	Description
mode	forecast (default), warning, or overview. Case-insensitive.
prefecture	One of the 47 prefectures — English name ("Tokyo"), Japanese ("東京都"), or JIS code ("13"). Required unless areaCode is set.
areaCode	Optional 6-digit JMA office code (e.g. "130000"); overrides prefecture. Needed for individual Hokkaido regions (prefecture Hokkaido defaults to the Sapporo office 016000).
maxItems	Max area records to output, 1–500 (default 100).
maxApiRequests	Hard per-run request cap, 1–20 (default 6).
proxyConfiguration	Apify proxy; default is a direct connection.

Values are validated before the first request; an invalid value fails the run immediately with a message that lists the valid values.

Common input mistakes

Mistake	Correct
"prefecture": "Osaka-shi" / "Yokohama" (a city)	"prefecture": "Osaka" / "Kanagawa" — prefectures only
"prefecture": "Tokio"	"prefecture": "Tokyo" (standard Hepburn spelling; Tōkyō, Tokyo-to are also accepted)
"mode": "weather"	"mode": "forecast" (or warning / overview)
"areaCode": "13"	"areaCode": "130000" (6 digits) — or leave it empty and set prefecture
"maxItems": "all"	a number, e.g. 100
Wanting Kushiro/Asahikawa forecasts with "prefecture": "Hokkaido"	set "areaCode" to that office (e.g. "014100" 釧路・根室, "012000" 上川・留萌)

Empty results?

A valid prefecture always yields at least one record in every mode (warning mode emits a record per area with hasActiveWarning: false when nothing is in force). Zero records only happen when areaCode is a code JMA does not publish a feed for (e.g. a sub-area code instead of an office code) — the run then ends with 0 items and a warning in the log (or the upstream HTTP 404 error). Use prefecture instead, or take the office code from https://www.jma.go.jp/bosai/common/const/area.json (offices).

How it fetches (politeness)

A single sequential connection, ≥ 1.2 s between requests, exponential backoff on 429/5xx, and a hard per-run request budget. A normal run makes only ~2 requests (the area-name index plus one feed). The Actor never evades a block: on a persistent 429 it fails visibly rather than hammering the server.

Attribution, terms & disclaimer

• Public open data. JMA website content is provided under the 公共データ利用規約（第1.0版）(Public Data License 1.0), which permits copying, adaptation, and commercial use provided the source is displayed. The required credit — 出典：気象庁 — is embedded verbatim in every record's license field. See the JMA terms of use.
• Unofficial — not affiliated. This is an independent tool. It is not affiliated with, endorsed by, or operated by the Japan Meteorological Agency.
• Edited / adapted. Per the terms, note that this tool edits and adapts JMA data (structuring Japanese data into English); it does not present the data as if produced by JMA. It redistributes JMA-published values; it is not a forecasting service (気象業務法第17条) and does not itself issue warnings (第23条). For life-safety decisions, always consult the official JMA site.
• Your responsibility. You are responsible for your own compliance with the JMA website terms and any applicable law (including data-protection law such as the GDPR) in how you use the output. The data is aggregate meteorology and contains no personal data.

Search terms

japan weather api · jma forecast data · japan weather warnings english · japan meteorological data · 気象庁 json · japan weather forecast scraper · tokyo weather api · japan rain probability · japan weather alerts