How Cold Is Too Cold to Swim Outside?

As the weather warms up, you might be itching to jump into a pool or take a dip in the ocean. But before you dive in, it’s essential to know how cold is too cold for swimming.

Even though everyone has a different tolerance levels to cold, a good rule of thumb is that water that is 70°F (21°C) or below is too cold to swim in without a wetsuit. Either wear a wetsuit under those conditions, or swim in water that is around 80°F (27°C) to stay warm and comfortable.

How Cold Is Too Cold to Swim

In this article, we’ll explore the ideal water temperatures for swimming, the risks associated with staying in cold water for too long, and how you can tell when it’s too cold to swim.

The Effect of Cold on the Human Body

Cold Shock Response

If you were wondering if there is a clear sign that the water is definitely too cold for you, then the cold shock response is your body’s way of communicating that to you.

The moment you dive into cold water, there is a good chance you can trigger the cold shock response, which is an involuntary reaction that causes rapid and uncontrollable breathing, increased heart rate, and a spike in blood pressure.

When this happens, it can make it difficult for you to coordinate your movements, plus there is a chance that you might end up choking on water as you’re gasping for air, all of which increases the risk of drowning.

Regular cold water swimmers can condition their bodies over time, becoming more adept at controlling their breathing and reducing the shock response. However, for inexperienced cold water swimmers, don’t expect to overcome this natural response from your body.

One way to decrease the risk of experiencing cold shock is by gradually acclimating your body to the water temperature. Don’t jump into frigid water suddenly – instead, take your time entering the water, allowing your body to adjust to the cold. Or, even better: wear a wetsuit instead so that you can stay warm in the cold water.

If you keep on swimming for too long in cold water, especially without a wetsuit, then you will be at risk of hypothermia.

Hypothermia: The Body’s Response to Cold

Hypothermia is what happens when your body loses heat faster than it can produce it. Typically, our bodies have a core temperature of 98.6°F (37°C). Our body functions normally at that internal temperature.

Now, if the temperature starts dropping, there’s no guarantee your body will function properly. This is why hypothermia is concerning – and it can lead to serious health problems, or even become life-threatening if not addressed quickly.

The scary thing is, technically any water temperature below our core temperature can cause hypothermia. The colder the water temperature is relative to your core temperature, the faster you can get hypothermia.

Hypothermia Symptoms: What to Look Out For

Let’s talk about some of the signs of hypothermia. Early on, you might start shivering, feel tired, or a bit clumsy. You may even feel confused or have trouble making decisions – things that you usually wouldn’t think twice about suddenly become challenging.

If hypothermia continues to advance, you may notice your shivering stop, which may sound good, but it’s actually a sign your body is running out of energy and can’t keep up with the heat loss anymore. Your pulse could become weak, and your movements might slow down.

In the most extreme cases, it could even lead to a loss of consciousness – a death sentence if there aren’t other people around.

As for how quickly you can get hypothermia, that can vary depending on a few things, such as how cold it is, what you’re wearing, and even how tired you are. But in cold water, hypothermia can kick in surprisingly quickly, often in less than 30 minutes.

The table below lists the time until you lose consciousness, as well as the expected survival times in various water temperatures ranging from warm to freezing. This information was sourced from this website.

Expected Survival Time in Cold Water
Water Temperature Unconsciousness Expected Survival Time
>80°F (>26.7°C) indefinite indefinite
70–80°F (21–27°C) 3–12 hours 3 hours – indefinite
60–70°F (16–21°C) 2–7 hours 2–40 hours
50–60°F (10–16°C) 1–2 hours 1–6 hours
40–50°F (4–10°C) 30–60 minutes 1–3 hours
32.5–40°F (0–4°C) 15–30 minutes 30–90 minutes
<32°F (<0°C) under 15 minutes under 15–45 minutes

So, again, how do you know when it’s too cold to swim? Well, looking at the table, anything less than 80°F seems risky, as there is a possibility you can lose consciousness if you spend enough time in the water.

What Water Temperature Is Too Cold to Swim In?

Most organizations suggest a minimum water temperature of 70°F (21°C). So, any water temperature below that is too cold for the average person to swim in without the appropriate gear and training.

As the temperature drops below 70°F, the risk of hypothermia dramatically increases, especially if you’re in the water for an extended period. Even at 70°F, some people may still find that to be a little chilly, so a wetsuit may be necessary.

Remember, though, this isn’t an absolute rule, and it’s always best to listen to your body. Different people have different thresholds for water temperature tolerance. Generally, for safe and comfortable swimming, consider these guidelines:

  • For children, pregnant women, and older adults, aim for a water temperature range of 84°F to 86°F (29-30°C).
  • For adults engaged in moderate physical activity like lap swimming or water aerobics, a pool temperature between 78°F and 82°F (26-28°C) is more suitable (you’ll warm up as you exercise).

Water Temperature vs. Air Temperature

If you want to know when it’s too cold to swim and you don’t want to find out by literally dipping your toes in the water, then many people make the (sometimes incorrect) assumption that the water will be warm if it’s also warm outside.

In this section, we will discuss why water temperature can often differ greatly from the air temperature.

Why Water Temperature Differs From Air Temperature

Water has a higher heat capacity than air. In simpler terms, water can absorb a lot more heat than air before it starts to get hot. This is why the ocean doesn’t immediately boil under the hot summer sun or freeze over in winter. The large heat capacity of water allows it to moderate temperature changes better than air can.

Moreover, water is a better conductor of heat than air. This means when you’re in water, it draws heat away from your body much faster than air at the same temperature would. So, swimming in water that is 65°F (18°C) will feel much colder than being in air of the same temperature.

For this reason, even a water temperature that seems high, such as 80°F, can actually cause you to shiver if you stay in it for long enough, since it is still much lower than your core temperature of 98.6°F.

Temperature Fluctuations

Another factor you should consider is that water temperatures fluctuate less than air temperatures.

During the day, sunlight warms up both the air and the water. But as soon as the sun sets, the air cools down quickly, while the water retains its heat longer and cools down more slowly. This is why on a hot day, a lake or ocean may still feel cool in the morning, and at night, the water might feel warmer than the air.

While there is a correlation between air and water temperature, it’s not a direct one. Just because the air temperature is high doesn’t mean the water is automatically warm, especially in deeper bodies of water that take more time to heat up.

When Is It Too Cold to Swim Outside? The Verdict

Any water temperature below 70°F is too cold to swim in. Ideally, the water temperature should be closer to 80°F or higher to feel safe and comfortable to swim in, without a wetsuit, and for a prolonged period of time.

Do not rely on the air temperature as an accurate predictor of the water temperature. You can only be somewhat sure if the weather has remained stable for multiple days in a row, otherwise it’s hard to predict the water temperature since it takes longer for water to heat up and cool down.

If you trigger the cold shock response as soon as you dip your toes into the water, resulting in rapid and uncontrollable breathing and increased heart rate, then you know for sure the water is too cold.

Additionally, if you start to experience the symptoms of hypothermia: sluggishness, exhaustion, difficulty thinking, then you have stayed too long in the water and your core temperature has decreased. Exit the water immediately, change into dry clothes, wrap yourself up in a blanket, and drink some hot water. If your symptoms don’t go away, then seek medical attention.