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

December 14, 11:07

Trend:

decreasing

Yesterday:

66.3°F

Tomorrow:

65.3°F

Sunrise:

06:38

Sunset:

16:27

Day Length:

9 h. 49 min.

Isumi in December

Minimum:

56.7°F

Average:

61.8°F

Maximum:

65.7°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 0.4°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

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 67.4°F on 2018, while the historical minimum was 62.6°F on 2021.

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 shows a gradual cooling trend. The average temperature is expected to be 65.1°F, the minimum temperature may reach 64.7°F, and the maximum might stay at 65.8°F.

Daily water temperature in Isumi

Date	Current Year actual* / forecast**	last year	10 years average
Nov 30	71.8°F	67.2°F	67.9°F
Dec 1	70.4°F	67.0°F	67.8°F
Dec 2	69.3°F	67.0°F	67.2°F
Dec 3	69.2°F	66.3°F	67.1°F
Dec 4	66.0°F	66.7°F	66.9°F
Dec 5	65.0°F	65.8°F	66.2°F
Dec 6	65.3°F	66.8°F	66.2°F
Dec 7	66.4°F	66.9°F	66.1°F
Dec 8	68.5°F	67.4°F	66.3°F
Dec 9	69.0°F	64.3°F	66.1°F
Dec 10	68.7°F	65.6°F	66.3°F
Dec 11	68.2°F	65.2°F	66.4°F
Dec 12	67.4°F	63.8°F	65.8°F
Dec 13	66.3°F	65.5°F	65.8°F
Dec 14	65.5°F	64.8°F	65.1°F
Dec 15	65.3°F	64.3°F	64.9°F
Dec 16	65.8°F	65.8°F	65.4°F
Dec 17	65.2°F	64.9°F	64.7°F
Dec 18	64.9°F	64.8°F	64.5°F
Dec 19	64.8°F	64.3°F	64.3°F
Dec 20	64.7°F	63.1°F	64.3°F
Dec 21	64.8°F	63.5°F	64.4°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	67.8°F	8mi
Ichihara	59.1°F	27mi
Kisarazu	59.2°F	29mi
Chiba	59.1°F	30mi
Kimitsu	59.1°F	31mi
Futtsu	60.6°F	34mi
Honchō	57.2°F	40mi
Yokosuka	62.5°F	42mi
Kawasaki	58.6°F	44mi
Yokohama	59.3°F	45mi

* current water temperature in this city

** straight line distance from Isumi