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 18.9°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.

66.0

°F

December 15, 07:19

Trend:

stable

Yesterday:

66.2°F

Tomorrow:

66.5°F

Sunrise:

06:39

Sunset:

16:27

Day Length:

9 h. 48 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 66.0°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 1.1°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 rise 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 67.6°F on 2018, while the historical minimum was 62.2°F on 2022.

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. Over the next week, the forecast shows a steady trend, with temperatures staying close to the average of 65.7°F. Both minimum and maximum temperatures expected to be close to the average, offering a week of stable water conditions.

Daily water temperature in Isumi

Date	Current Year actual* / forecast**	last year	10 years average
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	65.9°F
Dec 14	66.2°F	64.8°F	65.1°F
Dec 15	66.0°F	64.3°F	64.9°F
Dec 16	66.5°F	65.8°F	65.4°F
Dec 17	65.9°F	64.9°F	64.7°F
Dec 18	65.6°F	64.8°F	64.5°F
Dec 19	65.5°F	64.3°F	64.3°F
Dec 20	65.4°F	63.1°F	64.3°F
Dec 21	65.5°F	63.5°F	64.4°F
Dec 22	65.5°F	63.4°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	67.4°F	8mi
Ichihara	59.6°F	27mi
Kisarazu	59.8°F	29mi
Chiba	59.6°F	30mi
Kimitsu	59.9°F	31mi
Futtsu	61.2°F	34mi
Honchō	58.0°F	40mi
Yokosuka	63.2°F	42mi
Kawasaki	59.1°F	44mi
Yokohama	60.2°F	45mi

* current water temperature in this city

** straight line distance from Isumi