Is Tokyo About to Reach 40°C? Visiting the Weather Station That Measures the City's Temperature

Where Is Tokyo's Temperature Actually Measured?

Summer has arrived once again.

In recent years, record-breaking heat has become common around the world, and Japan is no exception. Dangerous temperatures have already settled in across much of the country.

On July 21, 2026, Gifu and Aichi Prefectures recorded Japan's first temperatures of 40°C or higher this year. Not long ago, reaching 40°C was considered an extraordinary event that made national headlines only once every few years. Today, however, because of global warming, such temperatures are appearing somewhere in Japan almost every summer.

In Japan, hot days are officially classified into several temperature categories. Until recently, the highest category had been Mōshobi, meaning a day with a maximum temperature of at least 35°C. In April 2026, however, the Japan Meteorological Agency introduced a new category—Kokushobi  (literally, "severe heat day")—for days reaching 40°C or higher.

Japan's Official Temperature Categories

Natsubi (夏日 / Summer Day)	25°C or higher
Manatsubi (真夏日 / Midsummer Day)	30°C or higher
Mōshobi (猛暑日 / Extremely Hot Day)	35°C or higher
Kokushobi (酷暑日 / Severe Heat Day)	40°C or higher (introduced in 2026)

The events of July 21 marked the first real use of this new category, as authorities continued warning that dangerously high temperatures would persist across Japan.

Visiting Tokyo's Official Weather Station

The following day, July 22, I headed to Kitanomaru Park after climbing Kudanzaka Hill under exactly the kind of blazing sunshine the forecast had promised.

Next to the Nippon Budokan, the park forms a surprisingly green space above the surrounding city streets. In one corner of the park, a slightly raised area enclosed by a fence catches the eye.

This is where central Tokyo's official weather observations are made.

Inside the enclosure are instruments that measure temperature, humidity, wind speed, sunshine duration, rainfall, and other meteorological data around the clock. Although temperatures are measured at many locations across Tokyo, this site provides the official temperature for central Tokyo reported in weather forecasts.

The electronic display shows 35.7°C at the time of the visit. Tokyo's official high for that day was later announced as 36.1°C.

A nearby electronic display showed the temperature had already exceeded 35°C, officially making it a Mōshobi.

While taking photographs, my smartphone displayed a high-temperature warning and informed me that its GPS functions had been temporarily restricted to protect the device from overheating.

If this was still only considered a "Mōshobi," I found myself wondering just how dangerous a 40°C Kokushobi would actually feel.

Has Central Tokyo Ever Reached 40°C?

Yet central Tokyo has never officially recorded a temperature of 40°C.

Its highest temperature remains 39.5°C, recorded on July 20, 2004.

This applies only to central Tokyo. Elsewhere within Tokyo Metropolis, the inland city of Ome has already reached 40.8°C.

The highest temperatures ever recorded in central Tokyo are as follows:

Highest Temperatures Ever Recorded in Central Tokyo

1	39.5°C	July 20, 2004
2	39.1°C	August 3, 1994
3	39.0°C	July 23, 2018
4	38.7°C	August 15, 1996
5	38.3°C	August 11, 2013

Nearly all of the highest temperatures have occurred in relatively recent decades.

Days exceeding 38°C have also become noticeably more frequent, illustrating the clear warming trend affecting central Tokyo.

Why the Observation Site Was Moved

There is another interesting aspect to this story.

The current observation site at Kitanomaru Park has only been in use since 2014.

Previously, Tokyo's official temperature had been measured at the Japan Meteorological Agency's former headquarters in Otemachi. When the agency relocated, the observation site was moved approximately 900 meters away to its current location.

Because the site changed from a dense business district surrounded by office buildings to a greener park environment, some questioned whether temperatures might now be recorded slightly lower than before.

The Meteorological Agency itself acknowledged that differences in surroundings could affect observations depending on the season and the time of day. Before the relocation, both sites operated simultaneously to maintain continuity in the long-term climate record.

The comparison showed that summer maximum temperatures at Kitanomaru Park tended to be about 0.2–0.3°C lower, and the number of Mōshobi days was also slightly smaller.

Looking again at the historical rankings, only one temperature recorded after the 2014 relocation—the 39.0°C observed in 2018—appears among Tokyo's top five hottest days.

Of course, that alone cannot prove that the relocation changed Tokyo's records. Still, it is not unreasonable to wonder whether some of the city's recent hot summers might have ranked even higher had the observations still been made in Otemachi.

At the same time, the official temperature does not necessarily match what people actually experience while walking through Tokyo's streets.

The heat trapped between concrete buildings and asphalt roads by the urban heat island effect is very different from the environment surrounding the weather instruments inside Kitanomaru Park.

Perhaps, even without an official 40°C reading, many people in Tokyo have already experienced conditions that felt every bit as hot.

Tokyo Still Stops Just Short of 40°C

Central Tokyo's highest temperature has repeatedly climbed to the brink of 40°C, only to stop just short of the mark.

Yet now that 40°C temperatures are no longer unusual elsewhere in Japan—and a new official category, Kokushobi, has even been created—the barrier no longer feels untouchable.

Today, the instruments inside the quiet enclosure at Kitanomaru Park continue recording Tokyo's weather, just as they do every day.

The day they first display 40.0°C may no longer be far away.

That moment might even arrive this very summer.