All data are in degrees Fahrenheit

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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.
Sea temperature in Isumi now

71.0

°F

July 7, 03:46

Trend:

increasing

Yesterday:

70.7°F

Tomorrow:

71.2°F

Sunrise:

04:30

Sunset:

18:56

Day Length:

14 h. 26 min.

Isumi in July

Minimum:

58.8°F

Average:

62.3°F

Maximum:

66.0°F

Sea water temperature in Isumi today

As of now, in Isumi, the water temperature is 71.0°F. Swimming in water of this temperature is seen as relatively warm and enjoyable for some individuals, although many might find it slightly too cool. Today's reading is 2.2°F lower 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 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 is also close to the historical minimum temperature for this date. The maximum temperature recorded for this date was 77.0°F on 2025, while the historical minimum was 70.3°F on 2022.

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 histoorical minimum and others when it was close to the historical maximum. The forecast for the upcoming week suggests a gradual increase. The average temperature is expected to rise up to 71.7°F, with minimum temperature starting at 71.2°F, while the maximum might reach 72.4°F.

Daily water temperature in Isumi

Date Current Year

actual* / forecast**

last year 10 years average
Jun 23 71.7°F 72.6°F 70.5°F
Jun 24 72.1°F 72.5°F 70.9°F
Jun 25 72.8°F 73.5°F 70.5°F
Jun 26 73.0°F 74.2°F 71.3°F
Jun 27 73.0°F 73.8°F 71.2°F
Jun 28 72.4°F 73.9°F 71.5°F
Jun 29 72.5°F 72.5°F 71.8°F
Jun 30 71.4°F 71.5°F 71.5°F
Jul 1 71.3°F 73.2°F 71.9°F
Jul 2 71.9°F 74.6°F 71.8°F
Jul 3 71.8°F 72.9°F 72.2°F
Jul 4 71.2°F 73.8°F 72.2°F
Jul 5 71.6°F 72.5°F 72.4°F
Jul 6 70.7°F 73.3°F 72.9°F
Jul 7 71.0°F 77.0°F 73.2°F
Jul 8 71.2°F 76.0°F 73.5°F
Jul 9 71.5°F 77.1°F 73.7°F
Jul 10 71.2°F 76.9°F 73.4°F
Jul 11 71.6°F 77.1°F 73.9°F
Jul 12 71.7°F 77.5°F 74.0°F
Jul 13 72.2°F 79.9°F 74.4°F
Jul 14 72.4°F 79.1°F 74.7°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 73.5°F 8mi
Ichihara 74.9°F 27mi
Kisarazu 74.3°F 29mi
Chiba 75.0°F 30mi
Kimitsu 74.3°F 31mi
Futtsu 74.0°F 34mi
Honchō 75.4°F 40mi
Yokosuka 73.9°F 42mi
Kawasaki 74.8°F 44mi
Yokohama 74.5°F 45mi

* current water temperature in this city

** straight line distance from Isumi