According to the National Center for Cold Water Safety, water temperatures below 70 degrees Fahrenheit should be treated with caution. Water temperatures between 50 and 60 degrees Fahrenheit makes it difficult to control your breathing, and anything lower than 40 degrees is painfully cold.

In 2026, safety guidelines from organizations like the National Center for Cold Water Safety suggest that any water temperature below 21°C (70°F) can feel uncomfortably cold to the average person. However, the "danger zone" begins at 15°C (60°F) and below. At these temperatures, the risk of "Cold Water Shock" is high; this is an involuntary gasp and rapid breathing that can lead to drowning if your head is submerged. If you are swimming in water between 10°C and 15°C, most experts recommend a wetsuit for anything longer than a few minutes. Water below 10°C (50°F) is considered "very cold" and can lead to incapacitation (the loss of muscle control in your arms and legs) within 15 to 30 minutes, even for experienced swimmers. For recreational pool swimming, the "Goldilocks" zone for comfort is typically 25°C to 28°C (77°F–82°F). For open-water swimmers in 2026, the "Rule of 100" is a popular safety measure: if the combined temperature of the air and the water is less than 100°F (37.7°C), you should strictly use a wetsuit and never swim alone due to the risk of hypothermia.