How Cold is the Water, and is it Really Dangerous?

April 10, 2026

After the lake ice recedes and springtime brings warmer temperatures, you may forget how cold and dangerous the water still is. Water does not warm as quickly as air; it takes weeks to months to warm to safe levels. Any water colder than 70F, a temperature that we do not expect until July, is dangerous - even a brief immersion of less than one minute can lead to cold water shock and death. In the Gulf of Maine, sea surface temperatures never warm above 70F all year and are dangerous for boaters and paddlers all season. Almost every spring, there are multiple drowning deaths in Maine and New Hampshire, where cold water is a contributing factor.

Here are some average water temperatures, by month, in Maine:

  • April: 40F average temperatures on inland waters and the ocean.
  • May: 50F in early May; 60F in late May.
  • June: 60F in early June; 70F in late June
  • July: 70F and higher.

Remember:

  • Know the water's actual temperature. Do not forecast water temperature by air temperature.
  • Water conducts heat away from your skin four times faster than air, because of its higher density. Your body will become dangerously cold very quickly; your muscles will cool, numb, and become unresponsive, leading to hypothermia. Drowning can happen very quickly.
  • Below 70F, the colder the water is, the more dangerous it becomes.
  • Cold water shock is extreme at 55F and below.

Signs of Cold Water Shock:

  • Gasping for Breath & Rapid Breathing
  • Sudden Spike in Heart Rate and Blood Pressure
  • Cognitive Impairment

What to do if someone is in Cold Water Shock:

  • Call 911
  • Gradually warm the person in cold water shock:
    • Remove their wet clothing and replace them with dry clothes.
    • Cover them with dry blankets
    • Use a hat and scarf to cover the head and neck.
  • Seek contact with dry, warm surfaces that are close to normal body temperature, 98.6F (between 35C and 45C)

Safety Tips:

  • Know the water temperature and stay aware of weather conditions.
  • Wear a life jacket.
  • Wear a wetsuit or drysuit based on conditions.
  • Know the signs of Cold Water Shock and Hypothermia.

Further Reading:

Synopsis of the Gray, Maine National Weather Service article, Learn Why Cold Water is so Dangerous!, released on April 5, 2026, for Cold Water Safety Awareness Week. Read the full article.

~ Sean Vaillancourt, Maine State Park Lifeguard Coordinator & Manager of Popham Beach State Park