# Karatsu Temperature, Rainfall and Sea Temperature Data: Annual Mean, Hot Days, Precipitation and Sea Surface Trends

By Karatsu Farm & Food (Karatsu Data Bank) / HTML: https://karatsu-f-f.com/en/karatsu-climate-data.html / Published 2026-11-07
- Karatsu annual mean temperature (2024): 17.9°C. Highest year in 2011-2025
- Days at or above 35°C in Karatsu (2024): 23 days. 0 to 1 day a year in 2011-2015
- Rise in Saga annual mean temperature: 1.7°C. per 100 years (since 1891)
- Rise in sea surface temperature, northern East China Sea: +1.37°C. per 100 years (1900-2025)

## How has the annual mean temperature in Karatsu changed?

**At the Japan Meteorological Agency (JMA) observation point in Karatsu (AMeDAS, Karatsu City, 23 m above sea level), the annual mean temperature was 16.0°C in 2011 and 17.9°C in 2024, the highest of the 15 years from 2011 to 2025. It was 17.2°C in 2025. The highest temperature in these 15 years was 37.5°C in 2025 ([JMA, Past weather data: Karatsu, annual values](https://www.data.jma.go.jp/stats/etrn/view/annually_a.php?prec_no=85&block_no=1610&year=&month=&day=&view=)).**

This page was made by Karatsu Farm & Food, a nonprofit in Karatsu, Saga, as part of the Karatsu Data Bank. It lists temperature and rainfall in Karatsu and the temperature of the surrounding seas, as published by JMA and Saga Prefecture. No conclusions or judgements are added.

Annual values for the Karatsu point start in 2010, and 2010 is marked as incomplete, so this page uses 2011 onwards. A record of more than 100 years exists at the Saga Local Meteorological Office in Saga City. Comparing the same years, Karatsu was 0.4 to 0.9°C cooler than Saga (our calculation; [JMA, Saga, annual values](https://www.data.jma.go.jp/stats/etrn/view/annually_s.php?prec_no=85&block_no=47813&year=&month=&day=&view=)).

Annual mean temperature, Karatsu (AMeDAS). Bars start at 14°C (our drawing), so bar lengths are not proportional to temperature. Source: [JMA, Past weather data: Karatsu, annual values](https://www.data.jma.go.jp/stats/etrn/view/annually_a.php?prec_no=85&block_no=1610&year=&month=&day=&view=).

| Year | Karatsu annual mean | Karatsu mean daily max | Karatsu mean daily min | Karatsu highest | Karatsu lowest | Saga annual mean |
|---|---|---|---|---|---|---|
| 2011 | 16.0°C | 20.2°C | 12.5°C | 34.1°C | -3.5°C | 16.6°C |
| 2012 | 15.9°C | 19.9°C | 12.5°C | 36.2°C | -4.3°C | 16.5°C |
| 2013 | 16.5°C | 20.5°C | 12.8°C | 35.2°C | -2.4°C | 17.1°C |
| 2014 | 16.2°C | 20.1°C | 12.7°C | 34.1°C | -1.4°C | 16.7°C |
| 2015 | 16.3°C | 20.2°C | 12.9°C | 34.6°C | -2.2°C | 17.1°C |
| 2016 | 17.1°C | 21.1°C | 13.6°C | 35.7°C | -4.6°C | 17.9°C |
| 2017 | 16.6°C | 20.7°C | 12.8°C | 36.1°C | -2.9°C | 17.0°C |
| 2018 | 16.7°C | 20.9°C | 13.0°C | 36.5°C | -2.6°C | 17.4°C |
| 2019 | 17.0°C | 21.3°C | 13.3°C | 35.3°C | -0.5°C | 17.7°C |
| 2020 | 17.0°C | 21.2°C | 13.3°C | 36.7°C | -0.9°C | 17.5°C |
| 2021 | 17.0°C | 21.5°C | 13.3°C | 35.0°C | -3.0°C | 17.9°C |
| 2022 | 16.9°C | 21.6°C | 13.1°C | 37.3°C | -2.8°C | 17.7°C |
| 2023 | 17.3°C | 22.1°C | 13.6°C | 37.0°C | -3.6°C | 18.1°C |
| 2024 | 17.9°C | 22.3°C | 14.4°C | 37.3°C | -1.6°C | 18.8°C |
| 2025 | 17.2°C | 22.1°C | 13.4°C | 37.5°C | -2.4°C | 18.0°C |

Sources: [JMA, Past weather data: Karatsu, annual values](https://www.data.jma.go.jp/stats/etrn/view/annually_a.php?prec_no=85&block_no=1610&year=&month=&day=&view=); [JMA, Saga, annual values](https://www.data.jma.go.jp/stats/etrn/view/annually_s.php?prec_no=85&block_no=47813&year=&month=&day=&view=). The Saga normal (1991-2020) is 16.9°C ([JMA, Saga, normals](https://www.data.jma.go.jp/stats/etrn/view/nml_sfc_ym.php?prec_no=85&block_no=47813&year=&month=&day=&view=)).

## How many days above 35°C does Karatsu have?

Counting from JMA daily values for Karatsu, days with a maximum of 35°C or more numbered 23 in 2024, 13 in 2022 and 12 in 2025, against 0 to 1 a year in 2011-2015. Days at or above 30°C numbered 89 in 2025, and days with a minimum of 25°C or more numbered 52 in 2024 (our count; [JMA, Past weather data: Karatsu, daily values](https://www.data.jma.go.jp/stats/etrn/view/daily_a1.php?prec_no=85&block_no=1610&year=2024&month=8&day=&view=p1), e.g. August 2024).

Days with a maximum temperature of 35°C or more, Karatsu (AMeDAS). Counted by us from daily values for May to October (including values JMA marks as quasi-normal). Source: [JMA, Past weather data: Karatsu, daily values](https://www.data.jma.go.jp/stats/etrn/view/daily_a1.php?prec_no=85&block_no=1610&year=2024&month=8&day=&view=p1).

| Year | Max 35°C or more (days) | Max 30°C or more (days) | Min 25°C or more (days) |
|---|---|---|---|
| 2011 | 0 | 66 | 15 |
| 2012 | 1 | 54 | 22 |
| 2013 | 1 | 56 | 34 |
| 2014 | 0 | 28 | 8 |
| 2015 | 0 | 26 | 8 |
| 2016 | 3 | 51 | 23 |
| 2017 | 2 | 60 | 34 |
| 2018 | 6 | 63 | 30 |
| 2019 | 1 | 47 | 20 |
| 2020 | 4 | 49 | 26 |
| 2021 | 1 | 56 | 14 |
| 2022 | 13 | 76 | 34 |
| 2023 | 7 | 76 | 28 |
| 2024 | 23 | 84 | 52 |
| 2025 | 12 | 89 | 35 |

Our counts from daily values for May to October; not day-count statistics published by JMA. Source: [JMA, Past weather data: Karatsu, daily values](https://www.data.jma.go.jp/stats/etrn/view/daily_a1.php?prec_no=85&block_no=1610&year=2024&month=8&day=&view=p1).

Saga Prefecture's booklet of climate adaptation techniques (June 2026) gives the 10-year average number of days at or above 35°C in August as 13.3 in Saga City and 3.9 in Karatsu City, and says summer temperatures in Karatsu run about 1 to 2°C below Saga City ([Saga Prefecture, Climate change adaptation techniques for agriculture, forestry and fisheries](https://www.pref.saga.lg.jp/kiji003115086/3_115086_394204_up_k8aihv3j.pdf), p.1).

| Month | Karatsu mean | Karatsu mean daily max | Karatsu days 35°C+ | Karatsu rainfall | Saga mean | Saga mean daily max | Saga days 35°C+ | Saga rainfall |
|---|---|---|---|---|---|---|---|---|
| Jun | 22.6°C | 26.7°C | 0.0 | 234.1 mm | 24.1°C | 28.6°C | 0.4 | 303.0 mm |
| Jul | 26.7°C | 30.7°C | 1.5 | 309.3 mm | 27.9°C | 32.1°C | 6.0 | 421.7 mm |
| Aug | 27.8°C | 32.1°C | 3.9 | 316.1 mm | 29.0°C | 33.7°C | 13.3 | 345.3 mm |
| Sep | 24.3°C | 28.2°C | 0.6 | 255.8 mm | 25.6°C | 30.0°C | 2.2 | 197.2 mm |
| Oct | 19.3°C | 23.5°C | 0.0 | 102.8 mm | 19.9°C | 24.8°C | 0.0 | 95.3 mm |

Average of the past 10 years (the years are not stated in the booklet), based on JMA past weather data. Source: [Saga Prefecture, Climate change adaptation techniques for agriculture, forestry and fisheries](https://www.pref.saga.lg.jp/kiji003115086/3_115086_394204_up_k8aihv3j.pdf) (June 2026), p.1.

## How much rain falls in Karatsu?

Annual precipitation at Karatsu (AMeDAS) in 2011-2025 ranged from 1,301.0 mm (2022) to 2,513.5 mm (2016). The largest daily total was 264.0 mm (2021) and the largest hourly total 77.5 mm (2024) ([JMA, Past weather data: Karatsu, annual values](https://www.data.jma.go.jp/stats/etrn/view/annually_a.php?prec_no=85&block_no=1610&year=&month=&day=&view=)). The normal annual precipitation at Saga (1991-2020) is 1,951.3 mm ([JMA, Saga, normals](https://www.data.jma.go.jp/stats/etrn/view/nml_sfc_ym.php?prec_no=85&block_no=47813&year=&month=&day=&view=)).

Annual precipitation, Karatsu (AMeDAS). Bar lengths drawn by us. Source: [JMA, Past weather data: Karatsu, annual values](https://www.data.jma.go.jp/stats/etrn/view/annually_a.php?prec_no=85&block_no=1610&year=&month=&day=&view=).

| Year | Annual precipitation | Largest daily | Largest hourly |
|---|---|---|---|
| 2011 | 1,948.5 mm | 100.0 mm | 32.0 mm |
| 2012 | 1,956.5 mm | 183.0 mm | 57.5 mm |
| 2013 | 2,088.0 mm | 204.0 mm | 49.0 mm |
| 2014 | 1,906.5 mm | 118.0 mm | 62.0 mm |
| 2015 | 1,959.5 mm | 92.5 mm | 31.5 mm |
| 2016 | 2,513.5 mm | 179.5 mm | 49.0 mm |
| 2017 | 1,532.5 mm | 146.5 mm | 70.0 mm |
| 2018 | 1,653.0 mm | 214.5 mm | 46.5 mm |
| 2019 | 1,794.0 mm | 216.5 mm | 49.0 mm |
| 2020 | 2,440.5 mm | 232.0 mm | 44.5 mm |
| 2021 | 2,283.0 mm | 264.0 mm | 53.0 mm |
| 2022 | 1,301.0 mm | 101.5 mm | 43.5 mm |
| 2023 | 2,017.5 mm | 195.5 mm | 68.0 mm |
| 2024 | 2,050.0 mm | 132.0 mm | 77.5 mm |
| 2025 | 1,502.5 mm | 98.0 mm | 35.5 mm |

Source: [JMA, Past weather data: Karatsu, annual values](https://www.data.jma.go.jp/stats/etrn/view/annually_a.php?prec_no=85&block_no=1610&year=&month=&day=&view=).

The leaflet Climate change in Saga Prefecture (March 2025) estimates from observations that a once-in-100-years daily rainfall at Saga is about 364 mm. It projects that by the end of the 21st century, compared with the end of the 20th, the yearly number of hourly rainfalls of 50 mm or more in northern Kyushu will be about 1.6 times under a 2°C scenario and about 2.8 times under a 4°C scenario ([Saga Local Meteorological Office and Fukuoka Regional Headquarters, Climate change in Saga Prefecture](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/leaflet/saga.pdf)).

## How much has Saga warmed over 100 years?

The Saga Local Meteorological Office and the Fukuoka Regional Headquarters of JMA state that the annual mean temperature at Saga has risen by 1.7°C per 100 years ([Saga Local Meteorological Office and Fukuoka Regional Headquarters, Climate change in Saga Prefecture](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/leaflet/saga.pdf)). Averaging the Saga series published by the Fukuoka Regional Headquarters (1891-2025) by decade gives 15.36°C for 1891-1900, 17.15°C for 2011-2020 and 18.10°C for the five years 2021-2025 (our calculation). The warmest year in the record is 2024 at 18.8°C ([Fukuoka Regional Headquarters, Saga annual mean temperature data](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/csv/obs/SAGA_tmean_ann_obs.csv)).

Decade averages of the Saga annual mean temperature (2021-2025 is five years). Averages calculated by us; bars start at 14°C. The Fukuoka Regional Headquarters series corrects data from before the station moved. Sources: [Saga annual mean temperature (CSV)](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/csv/obs/SAGA_tmean_ann_obs.csv); [Fukuoka Regional Headquarters, Observed climate change in Kyushu and Yamaguchi](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/observation.html).

## How much have the seas around Karatsu warmed?

JMA reports that the annual mean sea surface temperature around Japan has risen at +1.36°C per 100 years up to 2025, more than the global +0.63°C ([JMA, Long-term trend of sea surface temperature around Japan](https://www.data.jma.go.jp/kaiyou/data/shindan/a_1/japan_warm/japan_warm.html)). Of the sea areas JMA uses, the northern East China Sea shows +1.37°C (1900-2025) and the southwestern Sea of Japan +1.57°C (1901-2025). The Saga Prefecture leaflet uses the northern East China Sea for its sea temperature projection.

| Sea area | Trend (annual, per 100 years) | Winter (Jan-Mar) | Spring (Apr-Jun) | Summer (Jul-Sep) | Autumn (Oct-Dec) | Annual normal (1991-2020) | 2024 anomaly | 2025 anomaly |
|---|---|---|---|---|---|---|---|---|
| Northern East China Sea | +1.37°C (±0.23) | +1.65°C | +1.22°C | +0.93°C | +1.64°C | 19.64°C | +1.08°C | +0.97°C |
| Southwestern Sea of Japan | +1.57°C (±0.30) | +1.75°C | +1.58°C | +1.17°C | +1.82°C | 17.78°C | +1.43°C | +0.64°C |

Figures in brackets are 95% confidence limits; all trends are significant at 99% (as stated by JMA). Source: [JMA, data on long-term SST trends around Japan](https://www.data.jma.go.jp/kaiyou/data/shindan/a_1/japan_warm/japan_warm_data.html) (time series for the [northern East China Sea](https://www.data.jma.go.jp/kaiyou/data/shindan/a_1/japan_warm/cfig/data/areaC_SST.txt) and [southwestern Sea of Japan](https://www.data.jma.go.jp/kaiyou/data/shindan/a_1/japan_warm/cfig/data/areaE_SST.txt)).

Monthly water temperatures measured off Karatsu by Saga Prefecture's research vessel are on [Karatsu and Genkai landings and water temperature](https://karatsu-f-f.com/en/genkai-landings.html).

The Saga booklet says of the Genkai fishing grounds that seaweed beds are shrinking because high water temperatures hinder seaweed growth and southern grazing species are increasing ([Saga Prefecture, Climate change adaptation techniques for agriculture, forestry and fisheries](https://www.pref.saga.lg.jp/kiji003115086/3_115086_394204_up_k8aihv3j.pdf), p.27).

## How much hotter is it projected to get?

Based on Climate Change in Japan 2025 by MEXT and JMA, the leaflet Climate change in Saga Prefecture (March 2025) gives these projections for the end of the 21st century compared with the end of the 20th ([Saga Local Meteorological Office and Fukuoka Regional Headquarters, Climate change in Saga Prefecture](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/leaflet/saga.pdf)).

| Item | End of 20th century (observed) | End of 21st century, 2°C scenario | End of 21st century, 4°C scenario |
|---|---|---|---|
| Rise in Saga Prefecture annual mean temperature | - | about 1.3°C | about 4.1°C |
| Days of 35°C or more a year (Saga Prefecture average) | 3 | about 9 | about 29 |
| Nights with a minimum of 25°C or more a year (Saga Prefecture average) | 11 | about 28 | about 73 |
| Rise in annual mean SST, northern East China Sea | - | about 1.23°C | about 3.47°C |
| Hourly rainfall of 50 mm or more, northern Kyushu | - | about 1.6 times | about 2.8 times |

Source: [Saga Local Meteorological Office and Fukuoka Regional Headquarters, Climate change in Saga Prefecture](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/leaflet/saga.pdf) (March 2025).

## FAQ

### Q1. What is the annual mean temperature in Karatsu?

At the JMA observation point in Karatsu (AMeDAS), the annual mean temperature in 2011-2025 ranged from 15.9°C (2012) to 17.9°C (2024). It was 17.2°C in 2025.

### Q2. How many days a year reach 35°C in Karatsu?

Counting from JMA daily values for Karatsu, days with a maximum of 35°C or more numbered 23 in 2024, 13 in 2022 and 12 in 2025, against 0 to 1 a year in 2011-2015.

### Q3. How much rain falls in Karatsu in a year?

Annual precipitation at Karatsu (AMeDAS) ranged from 1,301.0 mm (2022) to 2,513.5 mm (2016) in 2011-2025. The Saga normal (1991-2020) is 1,951.3 mm.

### Q4. How much has Saga warmed over 100 years?

The Saga Local Meteorological Office and the Fukuoka Regional Headquarters of JMA state that the annual mean temperature at Saga has risen by 1.7°C per 100 years. The warmest year in the record is 2024 at 18.8°C.

### Q5. Are the seas around Karatsu getting warmer?

According to JMA, the annual mean sea surface temperature has risen at +1.37°C per 100 years in the northern East China Sea (1900-2025) and +1.57°C in the southwestern Sea of Japan (1901-2025), against +1.36°C for the seas around Japan as a whole.

## Sources

| Document | Publisher | Date | URL | Accessed |
|---|---|---|---|---|
| Past weather data: Karatsu, annual values | JMA | 2026-11 (updated) | [https://www.data.jma.go.jp/stats/etrn/view/annually_a.php?prec_no=85&block_no=1610&year=&month=&day=&view=](https://www.data.jma.go.jp/stats/etrn/view/annually_a.php?prec_no=85&block_no=1610&year=&month=&day=&view=) | 2026-11-07 |
| Past weather data: Karatsu, daily values (May-Oct 2011-2025) | JMA | 2026-11 (updated) | [https://www.data.jma.go.jp/stats/etrn/view/daily_a1.php?prec_no=85&block_no=1610&year=2024&month=8&day=&view=p1](https://www.data.jma.go.jp/stats/etrn/view/daily_a1.php?prec_no=85&block_no=1610&year=2024&month=8&day=&view=p1) | 2026-11-07 |
| Past weather data: Saga, annual values | JMA | 2026-11 (updated) | [https://www.data.jma.go.jp/stats/etrn/view/annually_s.php?prec_no=85&block_no=47813&year=&month=&day=&view=](https://www.data.jma.go.jp/stats/etrn/view/annually_s.php?prec_no=85&block_no=47813&year=&month=&day=&view=) | 2026-11-07 |
| Past weather data: Saga, normals (1991-2020) | JMA | 2021 | [https://www.data.jma.go.jp/stats/etrn/view/nml_sfc_ym.php?prec_no=85&block_no=47813&year=&month=&day=&view=](https://www.data.jma.go.jp/stats/etrn/view/nml_sfc_ym.php?prec_no=85&block_no=47813&year=&month=&day=&view=) | 2026-11-07 |
| Saga annual mean temperature 1891-2025 (CSV) | Fukuoka Regional Headquarters, JMA | 2026 | [https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/csv/obs/SAGA_tmean_ann_obs.csv](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/csv/obs/SAGA_tmean_ann_obs.csv) | 2026-11-07 |
| Observed climate change in Kyushu and Yamaguchi | Fukuoka Regional Headquarters, JMA | 2026 | [https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/observation.html](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/observation.html) | 2026-11-07 |
| Climate change in Saga Prefecture (leaflet) | Saga Local Meteorological Office and Fukuoka Regional Headquarters | 2025-03 | [https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/leaflet/saga.pdf](https://www.data.jma.go.jp/fukuoka/kaiyo/chikyu/report/leaflet/saga.pdf) | 2026-11-07 |
| Long-term trend of sea surface temperature around Japan | JMA | 2026-03-05 | [https://www.data.jma.go.jp/kaiyou/data/shindan/a_1/japan_warm/japan_warm.html](https://www.data.jma.go.jp/kaiyou/data/shindan/a_1/japan_warm/japan_warm.html) | 2026-11-07 |
| Data on long-term SST trends around Japan | JMA | 2026-03-05 | [https://www.data.jma.go.jp/kaiyou/data/shindan/a_1/japan_warm/japan_warm_data.html](https://www.data.jma.go.jp/kaiyou/data/shindan/a_1/japan_warm/japan_warm_data.html) | 2026-11-07 |
| Climate change adaptation techniques for agriculture, forestry and fisheries in Saga | Saga Prefecture | 2026-06 | [https://www.pref.saga.lg.jp/kiji003115086/3_115086_394204_up_k8aihv3j.pdf](https://www.pref.saga.lg.jp/kiji003115086/3_115086_394204_up_k8aihv3j.pdf) | 2026-11-07 |

## Notes on reading the figures

Karatsu figures come from an AMeDAS point and Saga figures from the Saga Local Meteorological Office; the two differ in location and height. Annual values for Karatsu start in 2010, and 15 years of values do not show a long-term trend. Day counts such as 35°C or more were counted by us from JMA daily values for May to October and are not figures published by JMA. The long Saga series from the Fukuoka Regional Headquarters corrects data from before the station moved, so early years can differ from the annual-values table. Sea surface temperatures are averages over whole sea areas, not coastal temperatures at Karatsu. The years behind the 10-year averages in the Saga booklet are not stated.

## What this page does not cover

Normals for the Karatsu point (we could not confirm a JMA normals table this time), other observation points in Karatsu City including former ones, month-by-month trends, typhoons, wind and sunshine, and the cost of warming to farming and fishing (farm figures are on [Karatsu agriculture data](https://karatsu-f-f.com/en/karatsu-agriculture-data.html)). This page does not cover our own projects.

## Citing this page and enquiries

To cite figures from this page or to ask about finding local data, please use the [contact page](https://karatsu-f-f.com/en/contact.html) or write to [info@karatsu-f-f.com](mailto:info@karatsu-f-f.com).

## About this page

By Hiroaki Kojima (Vice Director, [Karatsu Farm & Food](https://karatsu-f-f.com/en/index.html)) / Contact: [info@karatsu-f-f.com](mailto:info@karatsu-f-f.com) ([contact page](https://karatsu-f-f.com/en/contact.html)) / Published 7 November 2026 / Markdown: [karatsu-climate-data.md](https://karatsu-f-f.com/en/karatsu-climate-data.md)

This page is made together with AI. See [this data bank and AI](https://karatsu-f-f.com/en/data-bank.html#ai) for how.

## Related links


- ▶ [Karatsu Data Bank](https://karatsu-f-f.com/en/data-bank.html)
- ▶ [Karatsu agriculture data](https://karatsu-f-f.com/en/karatsu-agriculture-data.html)
- ▶ [Karatsu population data](https://karatsu-f-f.com/en/population-data.html)
- ▶ [日本語版](https://karatsu-f-f.com/karatsu-climate-data.html)