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 18.4°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.

65.1

°F

December 27, 18:56

Trend:

stable

Yesterday:

64.8°F

Tomorrow:

64.9°F

Sunrise:

06:45

Sunset:

16:33

Day Length:

9 h. 48 min.

Isumi in January

Minimum:

57.6°F

Average:

63.0°F

Maximum:

66.3°F

Sea water temperature in Isumi today

As of now, in Isumi, the water temperature is 65.1°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 0.8°F higher than the average recorded on this particular day in recent years. Since yesterday, there was a slight increase in temperature. This indicates a warming trend over the past day. According to the forecast, we expect the temperature to fall a bit.

Recent sea temperature and forecast

Today's water temperature is considerably lower than the average registered over the last two weeks, indicating a slight cooling trend. It also falls within the range of the average temperature recorded for this date, suggesting a consistent weather trend. The maximum temperature recorded for this date was 67.3°F on 2015, while the historical minimum was 61.0°F on 2022.

latest data

last year

The water temperature over the last two weeks displayed soome variability. While the two week average stayed close to the historical average, there were some days when the temperature was close to the maximum recorded over the past years. The forecast for the upcoming week shows a gradual cooling trend. The average temperature is expected to be 64.1°F, the minimum temperature may reach 63.5°F, and the maximum might stay at 64.9°F.

Daily water temperature in Isumi

Date	Current Year actual* / forecast**	last year	10 years average
Jan 1	63.8°F	62.5°F	63.0°F
Jan 2	63.8°F	61.3°F	63.0°F
Jan 3	63.5°F	60.7°F	62.7°F
Dec 13	66.3°F	65.5°F	65.9°F
Dec 14	66.2°F	64.8°F	65.2°F
Dec 15	64.0°F	64.3°F	64.8°F
Dec 16	67.2°F	65.8°F	65.5°F
Dec 17	67.6°F	64.9°F	65.0°F
Dec 18	68.1°F	64.8°F	64.8°F
Dec 19	68.0°F	64.3°F	64.7°F
Dec 20	65.8°F	63.1°F	64.5°F
Dec 21	65.6°F	63.5°F	64.5°F
Dec 22	65.5°F	63.4°F	64.5°F
Dec 23	65.9°F	60.6°F	64.0°F
Dec 24	65.4°F	63.1°F	63.8°F
Dec 25	65.2°F	65.2°F	63.6°F
Dec 26	64.8°F	65.2°F	64.1°F
Dec 27	65.1°F	64.3°F	64.3°F
Dec 28	64.9°F	63.9°F	64.1°F
Dec 29	64.6°F	63.5°F	63.8°F
Dec 30	64.2°F	62.9°F	63.4°F
Dec 31	64.1°F	62.4°F	63.4°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 108 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, 61.9°F in Spring, 74.2°F in Summer, and 73.9°F in Autumn.

Popular neighboring cities and resorts

City	Water temperature*	Distance**
Katsuura	67.0°F	8mi
Ichihara	54.4°F	27mi
Kisarazu	56.7°F	29mi
Chiba	53.7°F	30mi
Kimitsu	56.5°F	31mi
Futtsu	58.0°F	34mi
Honchō	52.6°F	40mi
Yokosuka	60.9°F	42mi
Kawasaki	54.5°F	44mi
Yokohama	56.2°F	45mi

* current water temperature in this city

** straight line distance from Isumi