What is the current water temperature in Isumi?

Q: What is the current water temperature in Isumi?

As of now, in Isumi, the water temperature is 18.62°C. Swimming in water of this temperature is generally concidered to be cool, and most people won't really enjoy it.

Japan > Isumi

Water temperature in Isumi

Detailed information about the current water temperature in Isumi. The trend over the last two weeks, daily averages, and precise forecast of the water temperature changes. Gain a deeper understanding of seasonal dynamics with monthly statistical analyses covering recent years.

65.5

°F

May 1, 20:57

Trend:

decreasing

Yesterday:

65.7°F

Tomorrow:

65.3°F

Sunrise:

04:48

Sunset:

18:24

Day Length:

13 h. 36 min.

Isumi in May

Minimum:

56.8°F

Average:

61.9°F

Maximum:

66.3°F

Sea water temperature in Isumi today

As of now, in Isumi, the water temperature is 65.5°F. Swimming in water of this temperature is generally concidered to be cool, and most people won't really enjoy it. Today's reading is 3.6°F higher than the average recorded on this particular day in recent years. The sea temperature remains approximately unchanged from yesterday. According to the forecast, we expect the temperature to fall a bit.

Recent sea temperature and forecast

The water temperature today is above average for the last two weeks, showing a small increase in temperature. It is also close to the historical maximum temperature for this date. The maximum temperature recorded for this date was 65.5°F on 2024, while the historical minimum was 59.6°F on 2025.

latest data

last year

Observations from the last two weeks indicate that the water temperature was in proximity to the highest values recorded on those days in the past. The forecast for the upcoming week suggests a gradual increase. The average temperature is expected to rise up to 66.0°F, with minimum temperature starting at 65.3°F, while the maximum might reach 66.8°F.

Daily water temperature in Isumi

Date	Current Year actual* / forecast**	last year	10 years average
Apr 17	59.9°F	57.1°F	60.5°F
Apr 18	60.3°F	57.0°F	60.8°F
Apr 19	62.0°F	55.9°F	61.1°F
Apr 20	65.1°F	53.1°F	61.3°F
Apr 21	67.0°F	56.4°F	61.8°F
Apr 22	65.7°F	58.0°F	62.1°F
Apr 23	66.1°F	58.9°F	62.3°F
Apr 24	66.4°F	59.5°F	62.5°F
Apr 25	66.3°F	60.0°F	62.8°F
Apr 26	66.5°F	61.4°F	63.5°F
Apr 27	67.0°F	59.8°F	63.4°F
Apr 28	66.4°F	61.7°F	62.9°F
Apr 29	65.6°F	61.8°F	62.5°F
Apr 30	65.7°F	59.1°F	62.2°F
May 1	65.5°F	59.6°F	62.0°F
May 2	65.3°F	60.2°F	61.7°F
May 3	65.6°F	60.9°F	62.1°F
May 4	65.8°F	61.2°F	62.2°F
May 5	65.9°F	60.9°F	62.3°F
May 6	66.2°F	61.5°F	62.7°F
May 7	66.7°F	62.3°F	63.2°F
May 8	66.8°F	61.4°F	63.2°F

* actual - actual temperature values

** forecast - projected values for the next week

Real-time coastal temperatures could deviate by several degrees from the provided readings. These deviations often become evident following intense rainfall or strong winds.

Our forecasting methodology leverages a mathematical model, that uses current water and weather conditions, historical records, wind intensity and direction.

Sea water temperature in Isumi by month

In Isumi, the months July through October offer comfortable swimming conditions, which amounts to 109 swimming days.

The warmest water in Isumi was recorded on August 17, 2024, reaching a 82.8°F. While the coldest temperature occurred on April 20, 2025, dipping to 53.1°F. The average readings by season are 62.1°F in Winter, 61.8°F in Spring, 74.2°F in Summer, and 74.0°F in Autumn.

Popular neighboring cities and resorts

City	Water temperature*	Distance**
Katsuura	66.7°F	8mi
Ichihara	64.1°F	27mi
Kisarazu	64.5°F	29mi
Chiba	64.1°F	30mi
Kimitsu	64.4°F	31mi
Futtsu	64.3°F	34mi
Honchō	64.3°F	40mi
Yokosuka	64.3°F	42mi
Kawasaki	65.2°F	44mi
Yokohama	64.5°F	45mi

* current water temperature in this city

** straight line distance from Isumi