水温(すいおん)

水温(すいおん) simply means "water temperature" — the temperature of water in any context.

Forms

• 水(すい) ("water") + 温(おん) (from 温度(おんど) "temperature") → 水温(すいおん)

Typical domains

• Marine and freshwater science (海(うみ)の水温(すいおん), 湖(みずうみ)の水温(すいおん))
• Aquarium hobby and fish farming
• Swimming and diving (pool and ocean temperatures)
• Hot baths and onsen (spring water temperatures)
• Automotive (水温(すいおん)計(けい): engine coolant-temperature gauge)
• Industrial and chemical processes

Common collocations

• 水温(すいおん)が上(あ)がる / 下(さ)がる: water temperature rises / falls
• 水温(すいおん)を測(はか)る: to measure water temperature
• 水温(すいおん)を保(たも)つ: to maintain a water temperature
• 水温(すいおん)計(けい): water-temperature gauge / thermometer
• 海面(かいめん)水温(すいおん): sea-surface temperature (a key meteorological / climate term)
• 適正(てきせい)水温(すいおん): optimal water temperature

Similar / related terms

• 気温(きおん): air temperature — the parallel word for ambient air
• 体温(たいおん): body temperature
• 室温(しつおん): room temperature
• 温度(おんど): temperature (general) — the umbrella term; 水温(すいおん) = 水(みず)の温度(おんど)
• 湯温(ゆおん): hot-water temperature — a closely related word focused on heated water (baths, kettles, hot springs); often more natural than 水温(すいおん) when the water is intentionally hot
• 海水温(かいすいおん): sea-water temperature — a more specific compound, common in marine science and weather news

Usage

• For an extremely hot bath or kettle, 湯温(ゆおん) is more idiomatic than 水温(すいおん): お風呂(ふろ)の湯温(ゆおん)は四十二(よんじゅうに)度(ど)です ("the bath temperature is 42 degrees").
• 水温(すいおん) is preferred when the water in question is naturally cool, when the temperature could be high or low, or when it is being measured/controlled in a technical setting.