What temperature should a hot tub be?

Between 100 and 104°F, the band Master Spas' manual calls safe for a healthy adult; it suggests lower temperatures for young children and for soaks longer than 10 minutes. 104°F is the ceiling in every source we read: CPSC says to keep spa water at or below it, and CDC says the same. Jacuzzi's 2025 J-300 manual describes an extended setting that reaches 106°F, above that guidance.

Check it now and then with a thermometer in the water. Master Spas' safety section says users should measure the water with an accurate thermometer before getting in. In 2023 CPSC announced a recall of some Jacuzzi and Sundance tubs whose temperature sensor could let the water run hotter than the set point; the remedy told owners to confirm 104°F or less with an external thermometer before entering. See hot tub recalls.

CDC says children under 5 should not use hot tubs. CDC says to talk to a healthcare provider before using a hot tub if you are pregnant. Anyone with a medical condition should ask a doctor first, as the makers' manuals also say.

Lower, if you'll be away a while. Hot Spring's manual says to drop to the lowest setting, about 80°F, for a trip of 5 to 14 days, partly because chlorine lasts substantially longer in cooler water. Bullfrog's economy modes drop the set point by 20°F while they are active. What holding temperature costs depends on the tub; see hot tub running cost and leaving a hot tub while away.