At what temperature does water become hot?


> 77 F > 25 CYou don’t need a wetsuit, unless you usually wear a wetsuit to jacuzzi, sauna, to the beach…
72F–77F 22C-25CShorty when it gets colder outside, like in the morning, evening and if it is windy. If the weather is warm, you still don’t need a wetsuit. You can also get away with a good wetsuit top/vest.
68F–72F 20C–22CThis is the comfortable bottom limit for surfing in shorty. Spring suit or 3/2 full suit is better for days without sun or if it gets windy.
64F–68F 18C–20CSpring suit or full suit 3/2. If you only have one wetsuit and it is 4/3 – no worries, you can also use it.
59F–64F 15C–18CA good 3/2 full suit is OK, but in the lower part of this range 4/3 wetsuit works better and in any weather.
54F–59F 12C–15CSomewhere in the middle of this range booties become necessary, at least if you like to feel you feet. A 4/3 wetsuit will work. If you will do a lot of surfing in water at the bottom of this temperature range, you should get a 5/3.
48F-54F 9C-12C5/3 or 5/4/3 wetsuit with booties. If it’s cold and windy also wear a hood and gloves. I hate wearing gloves so they are the last piece I put on.
< 48 F < 9 C5/3 can work, 6/5/4 is better, depends on how extreme do you want to get. Often it is not the thickness of the wetsuit, but bad booties, gloves etc that are the source of cold. So not only the wetsuit, also the booties, gloves and hood must be thick (at least 5mm).

With good equipment, there is no limit for cold water surfing. With all the possible combinations people often ask which wetsuit thickness should they buy? In my experience: “If you only get one wetsuit – get a 4/3!” It is the most versatile and useful in widest range of temperatures.

Two Cold and Wet Wetsuit ‘Tricks’

Since we finished the chart with some really cold water, here are also two useful tips for putting on a cold wet wetsuit.

  1. Wet wetsuit is harder to put on than dry, not just because of the great and enjoyable wet and cold feeling but also because it sticks to your skin and it won’t go on. So to do it faster, put a PVC bag on you leg or arm before you push it through your wetsuit. Your arms/legs will slide through the sleeves like a hot knife through butter.
  2. The other trick is to have a dry rash guard in store. Put it on before you get into a wet wetsuit and you won’t feel the cold neoprene on your body.

The final trick would be to just suck it up and get over it as quickly as possible and then get into the water and catch a few while your buddies are still whining in the parking lot :).

PS: The is one more chart in this article as well.

PPS: If you find this article and char useful please share it on FB/Twitter etc… Many tnx!


pH and Water Temperature

Water temperature can alter the number ions presen
Water temperature can alter the number ions present, changing the pH of the solution without making it more acidic or basic.

pH is calculated by the number of hydrogen ions in solution. At a pH of 7, the hydrogen and hydroxyl ions have equal concentrations, 1 x 10-7 M, keeping the solution neutral 27. However, these concentrations only hold true at 25°C. As the temperature increases or decreases, the ion concentrations will also shift, thus shifting the pH value 27. This response is explained by Le Chatelier’s Principle. Any change to a system at equilibrium, such as adding a reactant or altering the temperature, will shift the system until it reaches equilibrium again 28. The equation:

H20 H+ + OH-

is an exothermic reaction 28. That means if the temperature of water increases, the equation will shift to the left to reach equilibrium again. A shift to the left decreases the ions in water, increasing the pH. Likewise, if the temperature were to decrease, the equation would shift to the right, increasing the ionic concentration and decreasing pH.

The pH of pure water varies with temperature while
The pH of pure water varies with temperature while remaining perfectly neutral. Pure water only has a pH of 7.0 at 25 degrees Celsius.

However, that does not mean that temperature changes will make a solution more acidic or basic. Because the ratio of hydrogen and hydroxyl ions remains the same, the acidity of water does not change with temperature 28. Instead, the entire pH range shifts, so that neutral water will have a value other than 7. Pure water will remain neutral at 0°C (pH is 7.47), 25°C. (pH is 7.00) or 100°C. (pH is 6.14).

What Temperature Should Your Hot Tub Be?

Choosing the perfect temperature for your hot tub is more than just a personal preference, there are a handful of guidelines you should follow to ensure the best experience.

Temperature When In Use

Now while 104 degrees is the maximum temperature for most hot tubs, it’s important to note this is probably a little too hot for most people. In fact, most people will enjoy a hot tub the most when the water is at a comfortable 100 to 102 degrees.

But if you have children, especially young kids who love playing in your hot tub, it’s important to consider their needs. Children have a lower heat tolerance than we do, and they may be spending more than the recommended 10 to 15 minutes in the water.

If you have kids, my advice would be to set the hot tub somewhere between 95 to 98 degrees, to be on the safe side and reduce the chances they overheat in your hot tub.

Temperature When Not In Use (Idle)

When you’re not planning to use your hot tub for weeks or months on end, you have a couple of options to “idle” the system.

During summer, spring or autumn, it’s perfectly fine to turn the heat down on your hot tub.

I’ve found that 50 degrees is a suitable temperature for a short vacation, you’re keeping it barely warm without burning any unnecessary electricity, and you can kick the temperature back up when you do get home. The only downside is it may take a few hours to heat again to an operational temperature when you return.

If you’re planning a holiday for a few weeks, you may want to switch your hot tub heating off entirely, though you may be better off draining it to avoid any problems with chemical imbalances when you do get back.

During winter, I’d definitely not recommend idling your hot tub. Instead, you should drain and empty your hot tub completely. There’s just too much risk something goes wrong when it’s idle, and the temperature drops to a point where the water inside freezes.

You don’t want to be paying for expensive fixes to the hot tub because you tried to save a few bucks in heating costs.

Temperature For Different Health Conditions

Now we all know a good soak in a hot tub can help you relax, but there are a few conditions where you may want to check with your doctor before stepping in the water.

If you have a history of heart disease, circulatory or blood pressure problems, you should speak to your physician first. They are your best source of information, for your specific health concerns, and will be able to explain the right way to use your hot tub safely.

That being said, if you have any concerns at all, my advice would be to choose a lower temperature. 95 to 98 degrees is still very warm and comfortable, while significantly reducing the risks you’ll face after a soak in the water.

If you’re pregnant, you will need to be particularly careful with the temperature, because raising your body temperature above 102.2 degrees can cause birth defects in your unborn child. In this case, you’d want to set a temperature at 100 degrees and stay in for 10 minutes or less at a time.

Temperature In Different Weather Conditions

Depending on the particular season, changing the temperature ever so slightly can help you make the best use of your hot tub.

During winter and the colder months, you’re going to want to set your hot tub a little warmer than you would generally prefer. Because the cold air and wintery breeze will strip the heat from your hot tub, which needs to be offset by a higher temperature in the water. 102 to 104 degrees is a typical setting during winter.

During summer, you may, in fact, want the opposite. Because you’re looking to cool down (instead of warming up), I’ve actually found it’s quite nice to relax in water that’s been set closer to the 80 to 85-degree level. It’s very refreshing for a soak, without being cold, so you can also stay and enjoy the water for much longer in the pleasant weather.

What Factors Influence Water Temperature?

Water temperature can be affected by many ambient conditions. These elements include sunlight/solar radiation, heat transfer from the atmosphere, stream confluence and turbidity. Shallow and surface waters are more easily influenced by these factors than deep water 37.


Solar radiation is the greatest influence on water
Solar radiation is the greatest influence on water temperature.

The greatest source of heat transfer to water temperature is from sunlight 36. Sunlight, or solar radiation, is a form of thermal energy 45. This energy is then transferred to a water’s surface as heat, increasing the temperature of the water. This heat transfer is due to water’s relatively low albedo 44. Albedo is the determined quality of a surface’s ability to reflect or absorb sunlight. Water’s low albedo means that it absorbs more energy than it reflects 44. The result is a daily fluctuation in water temperature based on the amount of sunlight received by the water.

If a body of water is deep enough to stratify, sunlight will only transfer heat through the photic zone (light-reaching). Most of this energy (greater than half) is absorbed in the first 2 m of the water 14. This energy will continue to be absorbed exponentially until the light is gone. The photic zone varies in depth but can be up to 200 m deep in the oceans46. The depth of the photic zone is based on the amount of solids and other light-scattering elements present in the water. The temperature of water below the photic zone is generally only altered when the water is mixed 37. Thus shallower bodies of water tend to warm quicker and reach higher temperatures than deeper water bodies 1.


Rivers can appear to steam in winter when colder a
Rivers can appear to steam in winter when colder air flows over the warmer water. Photo Credit: Anthony DeLorenzo via Flickr

Atmospheric heat transfer occurs at the water’s surface. As heat always flows from a higher temperature to a lower temperature, this transfer can go both ways 6. When the air is cold, warm water will transfer energy to the air and cool off. This conduction can often be seen as fog or a “steaming” river 14. If the air is hot, cold water will receive the energy and warm up. The extent of this transfer is based on the thermal inertia and specific heat of water 14. Water temperature fluctuations are more gradual than air temperature fluctuations 14.


Turbidity monitoring during the Passaic river dred
Turbidity monitoring during the Passaic river dredge project. Turbidity can increase water temperatures.

Increased turbidity will also increase water temperature. Turbidity is the amount of suspended solids in water. These suspended particles absorb heat from solar radiation more efficiently than water 47. The heat is then transferred from the particles to water molecules, increasing the temperature of the surrounding water 47.


As the river flows into the lake, it can affect th
As the river flows into the lake, it can affect the temperature of the water. Photo Credit: Roberto Araya Barckhahn via Wikimedia Commons

Groundwater, streams and rivers can alter the temperature of the body of water into which they flow. If a spring or groundwater source is colder than the river it flows into, the river will become cooler. Recalling the rules of heat transfer (energy flows from hot to cold), the river loses energy to the cooler water as it warms it up 6. If the inflow is large or fast enough, the equilibrium temperature of the water will be close to the temperature of the inflow 1. Glacial fed streams will keep conjoining rivers cooler near the source of the flow than further downstream 1.

Man-made Influences

Thermal pollution from municipal and industrial ef
Thermal pollution from municipal and industrial effluents can negatively affect water quality. Photo credit: Vmenkov via Wikimedia Commons

Man-made influences on water temperature include thermal pollution, runoff, deforestation and impoundments.

Thermal Pollution Thermal pollution is any discharge that will dramatically alter the temperature of a natural water source 48. This pollution commonly comes from municipal or industrial effluents 1. If the temperature of discharge is significantly warmer than the natural water, it can negatively affect water quality. There are several significant consequences of thermal pollution, including diminished dissolved oxygen levels, fish kills and influxes of invasive species 48.

Runoff from parking lots and other impervious surfaces are another form of thermal pollution. Water that flows off of these surfaces absorb much of their heat and transfer it to a nearby stream or river, elevating the temperature 9.

Deforestation It is not only manmade additions that can affect water temperature. Water that is shaded by vegetation and other objects will not absorb as much heat as sunlit water 14. When trees or riparian canopies are removed, a body of water can become unusually warm, altering its natural cycle and habitats 48.


The McKenzie dam altered the water temperature pat
The McKenzie dam altered the water temperature pattern downstream, affecting fish behaviors, particularly reproduction.

Impoundments such as dams can drastically affect water temperature cycles. While a dam does not directly contribute heat to the water, it can affect the natural patterns of water temperature warming and cooling 9. An operational dam without a sliding gate assembly can alter the water temperatures downstream of the dam, which can affect local fish population behaviors.

Shifting the temperature pattern can affect the migration, spawning and hatching of local fish species 9. The temperature pattern will shift if the reservoir stratifies and the dam release is too high or too low, releasing unusually cool or unusually warm water into the stream 9.


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