Where does the data come from?

JMA’s published JSON, read directly by your browser. It does not pass through this site, and nothing is altered.

Does anyone learn which region I picked?

JMA’s servers see which region’s file was requested. Nobody else does, and the remembered choice stays in your browser.

Does it show warnings?

No — forecasts only. For warnings and evacuation guidance, consult JMA or your local authority directly.

When is the forecast updated?

JMA issues the prefectural forecast three times a day, at 05:00, 11:00 and 17:00, and the weekly outlook at 11:00 and 17:00. Extra updates go out when the picture changes substantially. This page reads the current file when you open it, so reopening after an issue time shows the new one.

A weather app disagrees with this.

Different sources. This displays the forecast exactly as JMA issued it; most apps blend their own model output, often including non-Japanese models, and pick locations differently. Neither is simply right — this is the one to check when you want the official position.

Can I see past weather?

No. The files read here are forecasts only and carry no observation record. For historical temperature and rainfall, use the past-data search published by JMA.

The chance of 1mm or more of rain, given per six-hour block. 30% means a three-in-ten chance of that much rain — not how hard or how long it will fall.

JMA grades the weekly outlook A to C for confidence. Later days are less reliable, and forecasts changing from one day to the next is ordinary.

The local meteorological observatory that produced the forecast. Which office covers which area is why some prefectures are split.

Occasional, brief, intermittent

These are defined terms, not everyday language. "In places" means less than half the area; "brief" means the condition runs continuously for under a quarter of the forecast period; "intermittent" means it comes and goes, totalling under half. So "intermittent rain" is not "it might drizzle" — it can mean rain for close to half the period.

The daily minimum is not always the morning

It is the lowest value between 00:00 and 24:00. When cold air arrives in the afternoon, the evening can be colder than the morning, and the stated minimum may be set at night. For how cold the morning will be, read the hourly forecast instead.

Why one prefecture gets several forecasts

Forecasts are issued per primary subdivision. Prefectures whose climate changes across mountains or coastline are split, and the north and south then carry different forecasts. JMA defines those boundaries, and they do not follow municipal ones — so the subdivision table published by JMA beats picking the nearest place name on a map.

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Weather forecast (JMA)

This tool fetches forecasts directly from the Japan Meteorological Agency (www.jma.go.jp). All that is sent is which region you looked at, and it does not pass through this site’s server. Your chosen region is stored in the browser only.

Shows the Japan Meteorological Agency’s published forecast as-is: today, tomorrow and the day after with rain probability, plus the seven-day outlook. Your region is remembered.

Region

Source: Japan Meteorological Agency

District names and the short forecast for today and tomorrow are published by the JMA in Japanese only, and are shown here exactly as issued — summarising them would drop how the weather changes through the day. The seven-day outlook is the one part rendered in English, from the numeric sky codes.

Output

Fetching the forecast…

The forecast is shown exactly as the Japan Meteorological Agency publishes it. Nothing is reworded, reinterpreted or adjusted to read better.

All tools

Why this one

The forecast text is not summarised: JMA issues the three-day forecast as prose, including qualifications about specific districts and times of day. Collapsing that into a single icon throws all of it away, so the original wording is shown.
Issue time and office are always shown: Forecasts age. Without knowing when the one you are reading was issued, it is easy to act on something stale, so the timestamp and issuing office sit under every result.
No keyed third-party service: The data is read straight from what JMA publishes. With no intermediary, the regions you look at are not handed to an advertising network.

How to use it

Choose a region
Any of the 58 JMA forecast divisions. Your choice is remembered next time.
Narrow it down
Some prefectures subdivide further — pick the district that applies to you.
Read
Detailed forecast for three days at the top, seven-day outlook below.

Terms and how to read them

Rain probability: The chance of 1mm or more of rain, given per six-hour block. 30% means a three-in-ten chance of that much rain — not how hard or how long it will fall.
Weekly confidence: JMA grades the weekly outlook A to C for confidence. Later days are less reliable, and forecasts changing from one day to the next is ordinary.
Issuing office: The local meteorological observatory that produced the forecast. Which office covers which area is why some prefectures are split.
Occasional, brief, intermittent: These are defined terms, not everyday language. "In places" means less than half the area; "brief" means the condition runs continuously for under a quarter of the forecast period; "intermittent" means it comes and goes, totalling under half. So "intermittent rain" is not "it might drizzle" — it can mean rain for close to half the period.
The daily minimum is not always the morning: It is the lowest value between 00:00 and 24:00. When cold air arrives in the afternoon, the evening can be colder than the morning, and the stated minimum may be set at night. For how cold the morning will be, read the hourly forecast instead.
Why one prefecture gets several forecasts: Forecasts are issued per primary subdivision. Prefectures whose climate changes across mountains or coastline are split, and the north and south then carry different forecasts. JMA defines those boundaries, and they do not follow municipal ones — so the subdivision table published by JMA beats picking the nearest place name on a map.

Questions

Where does the data come from?: JMA’s published JSON, read directly by your browser. It does not pass through this site, and nothing is altered.
Does anyone learn which region I picked?: JMA’s servers see which region’s file was requested. Nobody else does, and the remembered choice stays in your browser.
Does it show warnings?: No — forecasts only. For warnings and evacuation guidance, consult JMA or your local authority directly.
When is the forecast updated?: JMA issues the prefectural forecast three times a day, at 05:00, 11:00 and 17:00, and the weekly outlook at 11:00 and 17:00. Extra updates go out when the picture changes substantially. This page reads the current file when you open it, so reopening after an issue time shows the new one.
A weather app disagrees with this.: Different sources. This displays the forecast exactly as JMA issued it; most apps blend their own model output, often including non-Japanese models, and pick locations differently. Neither is simply right — this is the one to check when you want the official position.
Can I see past weather?: No. The files read here are forecasts only and carry no observation record. For historical temperature and rainfall, use the past-data search published by JMA.

Region

Output

Related tools

Why this one

How to use it

Choose a region

Narrow it down

Read

Terms and how to read them

Questions