The Japan Meteorological Agency publishes typhoon approach normals for thirteen areas of Japan. The 1991-2020 figure for the Okinawa region is 7.7 approaches a year, against 3.3 for the Kanto-Koshin region and 1.9 for Hokkaido. The same agency puts the normal rainy season for Okinawa at around 10 May to around 21 June, and the prefecture’s habu jellyfish advisory for 2026 ran from 1 June to 30 September.
The prefecture publishes three separate counts of its islands, and they are 691, 54 and 38
Okinawa does not have one island number. The Geospatial Information Authority of Japan announced on 28 February 2023 that it had counted the islands of Japan by taking islands recognised under laws and regulations together with naturally formed land enclosed by a coastline of 0.1 km or longer, checked against its electronic national base map as that map stood in January 2022; the prefecture’s own page records that the figure returned for Okinawa was 691.
A second and much smaller number comes from the law. Under Article 3, item 3 of the Act on Special Measures for the Promotion and Development of Okinawa and Article 1 of its enforcement order, the islands in question are those in Okinawa other than Okinawa Island, namely Miyakojima, Ishigakijima and other islands designated by the Prime Minister in consultation with the heads of the relevant administrative organs; the prefecture calls them collectively the designated remote islands. There are 54 of them: 38 inhabited and 16 uninhabited. Okinawa Island itself is counted separately, and 11 further islands are joined to it by bridges or similar links, 9 of them inhabited and 2 not.
The prefecture attaches three further figures to those 54 islands. Their population is 131,901, which it gives as about 8.9 per cent of the prefectural population of 1,485,670 on the resident register as at 1 January 2022; dividing one by the other returns 8.878 per cent, so the rounding is the prefecture’s. The area it gives for the designated remote islands and the like is 1,024.66 square kilometres, about 44.9 per cent of the prefectural total of 2,282.15 square kilometres, which it takes from the Geospatial Information Authority’s fiscal 2022 survey of areas by prefecture and municipality, compiled as at 1 July 2022; that division returns 44.90 per cent. Population density is 1,071 per square kilometre on Okinawa Island and 129 on the inhabited remote islands. Separately, the prefecture describes the sea area it occupies as roughly 1,000 km east to west and 400 km north to south, and calls that range comparable to two thirds of Honshu.
Typhoon approaches normally number 7.7 a year here, and the monthly figures do not add up to that
The Japan Meteorological Agency defines an approach as the centre of a typhoon coming within 300 km of any of its observatories in the region concerned. On that definition the 1991-2020 normal for the Okinawa region is 7.7 a year. The month-by-month normals are 0.0 in April, 0.4 in May, 0.6 in June, 1.5 in July, 2.2 in August, 1.9 in September, 1.1 in October, 0.3 in November and 0.0 in December.
Adding those nine figures gives 8.0, not 7.7. That is not an error in the table: the agency prints two notes above it saying that an approach can straddle two months, so the monthly totals and the annual figure do not necessarily agree, and that rounding produces the same effect. A third note covers the blank cells: a blank month is one in which the statistical period held no case at all, which is why the Okinawa row begins at April instead of January. A reader who sums the row will get a different answer from the one the agency publishes, and the agency says so in advance.
The wider grouping is published as well. The normal for Okinawa and Amami together is 7.9 a year, and for the four main islands the agency calls the mainland it is 5.8. The figure for the whole country is 11.7 approaches and 3.0 landfalls a year, out of 25.1 typhoons formed.
The table below reproduces all thirteen rows of the agency’s regional table. Two of its labels carry notes. The northern Kyushu region there includes Yamaguchi Prefecture and the Chugoku region does not, and the Kanto region excludes the Izu Islands and the Ogasawara Islands, which the agency lists as a row of their own.
| Region (JMA normal, 1991-2020) | Typhoon approaches per year |
|---|---|
| Okinawa region | 7.7 |
| Izu Islands and Ogasawara Islands | 5.4 |
| Amami region | 4.3 |
| Southern Kyushu | 3.9 |
| Northern Kyushu region | 3.8 |
| Tokai region | 3.5 |
| Kinki region | 3.4 |
| Shikoku region | 3.3 |
| Kanto-Koshin region | 3.3 |
| Chugoku region | 3.0 |
| Hokuriku region | 2.8 |
| Tohoku region | 2.7 |
| Hokkaido region | 1.9 |
The rainy season normally starts about 10 May and ends about 21 June, and 2026 ran outside both dates
The agency’s table of past rainy season dates for Okinawa, which begins in 1951, gives the normal as around 10 May for the start and around 21 June for the end. The word the table uses for every entry, normals included, is the equivalent of “around”. The agency explains why: entering and leaving the rainy season takes a transition of about five days on average, and the date printed is roughly the middle day of that transition. The dates here are also the settled statistics rather than the forecast-based announcements made during the season, because the agency reviews how the weather actually ran from spring into summer and fixes the dates afterwards. The normal is the 1991-2020 average, with any year whose dates could not be identified left out of it.
In 2026 the season was declared around 4 May and around 29 June, both outside the normal dates, and the column the agency heads as the area-average ratio to normal of rainy season precipitation reads 147. That column is not measured over the declared dates. The agency defines it as the two-month precipitation total for May and June in the case of Okinawa and Amami, using observations from meteorological observatories and weather stations across the country and averaging the ratio to normal within each region. In 2025 the same row reads around 5 May, around 7 June and 99 per cent. The three years before that were 187 per cent in 2024, 63 per cent in 2023 and 214 per cent in 2022, so the ratio moves across a wide band from one year to the next.
Naha’s monthly precipitation normals show where the water actually falls. June is the wettest month of the twelve at 284.4 mm, but September is close behind at 275.2 mm, and September sits in the typhoon months rather than the rainy season. May, the month the rainy season normally starts, comes third at 245.3 mm. The annual normal is 2,161.0 mm.
January is the coolest month in Naha at a mean of 17.3 degrees, and July is the warmest at 29.1
The figures below are the Japan Meteorological Agency’s normals for the Naha observation site, all from the 1991-2020 statistical period with 30 years of data behind every column. January is the lowest monthly mean at 17.3C and February is next at 17.5C. The lowest daily minimum normal is 14.9C, also in January. July has the highest monthly mean at 29.1C and August is 0.1 degree behind it at 29.0C. The annual mean is 23.3C.
| Month at Naha | Mean temperature (C) | Mean daily maximum (C) | Mean daily minimum (C) | Precipitation (mm) |
|---|---|---|---|---|
| January | 17.3 | 19.8 | 14.9 | 101.6 |
| February | 17.5 | 20.2 | 15.1 | 114.5 |
| March | 19.1 | 21.9 | 16.7 | 142.8 |
| April | 21.5 | 24.3 | 19.1 | 161.0 |
| May | 24.2 | 27.0 | 22.1 | 245.3 |
| June | 27.2 | 29.8 | 25.2 | 284.4 |
| July | 29.1 | 31.9 | 27.0 | 188.1 |
| August | 29.0 | 31.8 | 26.8 | 240.0 |
| September | 27.9 | 30.6 | 25.8 | 275.2 |
| October | 25.5 | 28.1 | 23.5 | 179.2 |
| November | 22.5 | 25.0 | 20.4 | 119.1 |
| December | 19.0 | 21.5 | 16.8 | 110.0 |
The same table gives Naha 0.0 snow days in each of the twelve months and in the annual row. Snowfall depth is printed as 0 cm for January and for the year, and as a dash for the other eleven months. Thunder is counted instead: the annual normal is 20.4 days with thunder, and the two highest months are June and August at 3.5 days each. Adding the twelve monthly figures returns 20.4 exactly, which is a check of the agency’s own arithmetic rather than a separate fact.
The jellyfish advisory covers 1 June to 30 September, and 6 of the 35 beaches that reported had no net
The prefecture issues a habu jellyfish outbreak advisory each year. Its English-language notice for 2026, dated 1 June 2026 and issued over the name of the Department of Public Health, Medical and Long-Term Care, gives the period as 1 June to 30 September 2026. The same notice states that in 2025 there were 199 incidents of people being stung or bitten by dangerous sea creatures and that 81 of them, approximately 40.7 per cent, were caused by habu jellyfish. Dividing 81 by 199 returns 40.70 per cent, which matches the figure the prefecture prints.
Alongside the advisory the prefecture publishes a table of beaches, headed with the note that it covers beaches that had reported as at 14 August 2026, that exclusion netting is sometimes taken out temporarily because of typhoons and the like, and that the current position should be checked with each beach’s manager individually. The table sorts the beaches by health centre and carries three columns for each: exclusion netting, a warning board, and vinegar. Counting the rows gives 35 beaches: 9 under the northern health centre, 8 under the central, 8 under the southern, 2 under Miyako and 8 under Yaeyama. Of those 35, exclusion netting is marked present at 29 and absent at 6; a warning board is present at 30 and absent at 5; vinegar is marked present at all 35. Those three counts are mine, taken by reading down the columns of the published table; the prefecture prints the marks but no totals.
The advisory’s own instructions are short. It asks swimmers to expose as little skin as possible and to stay inside the netted area, to bring vinegar to the beach, and, if stung, to leave the water without sudden movements, avoid scratching, pour vinegar over the sting, cool the area after removing tentacles, and then go to a hospital or clinic. It also places the duty of placing and checking the nets on beach custodians.
The prefecture also runs a reporting channel. Its page asks bathing beaches and municipalities to report sting and bite cases to the head of the health centre with jurisdiction on one form, excluding anyone carried off by emergency transport, and asks medical institutions to report on a second form; electronic submission is offered as well. The page gives the purpose as grasping the occurrence and the case information accurately so that the necessary preventive measures can be taken, and it does not say that the advisory’s own totals are drawn from that collection.
A separate prefectural page lists the annual hazard prevention project reports, running back to the volume covering fiscal 2003 to 2007. Its note records that the aggregated results for fiscal 2020, fiscal 2022 and fiscal 2023 were corrected on 9 July 2025 after omissions in the reported case counts came to light, that part of the text of the fiscal 2023 volume was amended, and that part of the text of the fiscal 2021 volume was amended too because of omissions in the year before it.
For the wider question of when arrivals to Japan cluster, our page on what the 2025 arrival figures show month by month sets out the national pattern.
Sources Checked
Okinawa Prefecture, Regional and Remote Islands Division – overview of the remote islands (page 1011854, updated 8 July 2025)
Confirmed the 54 designated remote islands split into 38 inhabited and 16 uninhabited, Okinawa Island counted separately and 11 bridge-linked islands of which 9 are inhabited and 2 are not, the designated islands’ population of 131,901 against a prefectural 1,485,670 on the resident register at 1 January 2022, the area of 1,024.66 square kilometres for the designated remote islands and the like against a prefectural 2,282.15 square kilometres from the Geospatial Information Authority survey compiled as at 1 July 2022, the densities of 1,071 and 129 per square kilometre, the east-west and north-south extents of about 1,000 km and 400 km and the comparison with two thirds of Honshu, the statutory definition in Article 3 item 3 and Article 1 of the enforcement order naming Miyakojima and Ishigakijima, and the Geospatial Information Authority count of 691 islands announced on 28 February 2023 using islands recognised under laws and regulations together with naturally formed land inside a coastline of 0.1 km or longer, checked against the electronic national base map as at January 2022.
https://www.pref.okinawa.jp/shigoto/kankotokusan/1011671/1011816/1011834/1011854.html
Japan Meteorological Agency – typhoon normals
Confirmed the 1991-2020 basis, the 300 km definition of an approach, the Okinawa region normal of 7.7 approaches a year and its monthly figures of 0.0, 0.4, 0.6, 1.5, 2.2, 1.9, 1.1, 0.3 and 0.0 from April to December, the three notes that a blank month held no case in the statistical period, that monthly and annual totals need not agree and that rounding affects the sums, the Okinawa and Amami figure of 7.9, the mainland figure of 5.8 with the mainland defined as Honshu, Hokkaido, Kyushu and Shikoku, all thirteen rows of the regional table at Izu and Ogasawara 5.4, Amami 4.3, southern Kyushu 3.9, northern Kyushu 3.8, Tokai 3.5, Kinki 3.4, Shikoku 3.3, Kanto-Koshin 3.3, Chugoku 3.0, Hokuriku 2.8, Tohoku 2.7 and Hokkaido 1.9, the notes that northern Kyushu includes Yamaguchi while Chugoku does not and that the Kanto region there excludes the Izu and Ogasawara Islands, and the national normals of 25.1 typhoons formed, 11.7 approaches and 3.0 landfalls.
https://www.data.jma.go.jp/yoho/typhoon/statistics/average/average.html
Japan Meteorological Agency – past rainy season dates for Okinawa
Confirmed that the table starts in 1951, the normals of around 10 May and around 21 June and their 1991-2020 basis excluding years whose dates could not be identified, the 2026 entry of around 4 May, around 29 June and 147, the 2025 entry of around 5 May, around 7 June and 99, the figures of 187, 63 and 214 for 2024, 2023 and 2022, the statement that the transition into and out of the rainy season averages about five days and that the printed date is roughly its middle day, the statement that these are settled rather than forecast-based dates, and the definition of the percentage column as the two-month May to June precipitation ratio to normal for Okinawa and Amami, averaged by region over observatories and weather stations nationwide.
https://www.data.jma.go.jp/cpd/baiu/kako_baiu01.html
Japan Meteorological Agency – climate normals for Naha
Confirmed the 1991-2020 statistical period and 30 years of data, every monthly figure in the table above, the annual mean of 23.3C, the annual precipitation of 2,161.0 mm, the 0.0 snow days in every month and in the year, the snowfall depth of 0 cm printed for January and for the year with a dash in the other eleven months, and the annual normal of 20.4 thunder days with 3.5 in June and 3.5 in August.
https://www.data.jma.go.jp/stats/etrn/view/nml_sfc_ym.php?prec_no=91&block_no=47936
Okinawa Prefecture – Habu Jellyfish Outbreak Advisory (2026), English version (PDF)
Confirmed the advisory period of 1 June to 30 September 2026, the date of 1 June 2026, the issuing Department of Public Health, Medical and Long-Term Care, the 199 incidents of stinging or biting by dangerous sea creatures in 2025 and the 81 of them at approximately 40.7 per cent caused by habu jellyfish, the prevention and first-aid instructions, and the responsibility placed on beach custodians for placing and checking the safety nets.
https://www.pref.okinawa.jp/_res/projects/default_project/_page_/001/005/048/r8english.pdf
Okinawa Prefecture – list of habu jellyfish measures by beach, covering beaches that had reported as at 14 August 2026 (PDF)
Confirmed the heading date of 14 August 2026, the notes on temporary removal of exclusion netting and on checking the current position with each beach manager, the sorting by health centre, the three columns of exclusion netting, warning board and vinegar, and the 35 rows grouped as 9 northern, 8 central, 8 southern, 2 Miyako and 8 Yaeyama, from which the counts of 29 and 6, 30 and 5, and 35 and none were read off.
https://www.pref.okinawa.jp/_res/projects/default_project/_page_/001/005/048/tyousa2.pdf
Okinawa Prefecture – habu jellyfish and dangerous marine life (page 1005048, updated 19 August 2026)
Confirmed that the advisory is issued for the June to September period each year, the 2026 heading of 1 June to 30 September, the 199 and 81 figures in the Japanese text, and the reporting arrangements under which bathing beaches and municipalities report on one form to the head of the health centre with jurisdiction excluding cases carried off by emergency transport, medical institutions report on a second form, electronic submission is available, and the stated purpose of the collection.
https://www.pref.okinawa.jp/kurashikankyo/petgaiju/1018721/1005068/1005048.html
Okinawa Prefecture – past habu jellyfish hazard prevention project reports (page 1005070, updated 17 April 2026)
Confirmed the list of annual reports running back to the volume for fiscal 2003 to 2007 and the note that the aggregated results for fiscal 2020, fiscal 2022 and fiscal 2023 were corrected on 9 July 2025 after omissions in the reported case counts, that part of the text of the fiscal 2023 volume was amended, and that part of the text of the fiscal 2021 volume was amended because of omissions in the preceding year.
https://www.pref.okinawa.jp/kurashikankyo/petgaiju/1018721/1005068/1005070.html
Last updated: September 2026
