Last week I was visiting Fargo to do some work with the Microsoft Business Frameworks team.  In the weeks leading up to the visit, our co-workers in North Dakota harassed us Redmond’ites with a variety of emails explaining how cold it had become.  Since I have now experienced -22 Fahrenheit (or feels like -47 with “wind chill”), I will be the first to admit that those warnings probably had some technical merit.  However, one of the emails suggested what seemed like a fanciful myth designed specifically to rattle us mild weather loving Washingtonians:


When the temperature is lower then -15 below zero, very hot water will vaporize immediately when thrown into the air.


After trying the experiment several times in person – I am now a believer.  It is one of the most bizarre things I have ever seen in person.   The interesting aspect to the experiment is that it does not happen with cold water.  However, even stranger then the actual phenomenon is that not one of my science educated co-workers can explain to me in exact terms why the phenomenon happens.  To me, that fact is even more bizarre since generally every computer science guy (including myself) fancies themselves as a renaissance man of the sciences.


However, I guess I can accept the fact that our collected amateur knowledge of physics has it limits. However, from what I can tell, there also seems to be nothing but speculation about the phenomenon on the web.  Thereby, it would be much appreciated if anyone can explain to me this phenomenon… until then I will just have to assume it is “magic”.


Comments (10)

  1. Rick Schaut says:

    Two words: vapor pressure. Not even a mystery.

  2. Louis Parks says:

    I don’t know about the physics issue, but I’m familiar with the termperature. I got stuck in North Dakota once. I think it was at least -10 that night. I was quite happy when I finally got back home to a "normal" winter of 10-30 degree temperaturs.

  3. Jorriss says:

    I know what you mean. Last week here in Miami I actually had to turn the air conditioner off. I hate the cold.

  4. Eric Holton says:

    I asked my father this question since he is a professor of atmospheric sciences at the U of W. Here is his reply:

    I am not sure about the specific

    number of -15 (I take it you are referring to -15 F rather than -15 C?)Anyway, my quick answer is that the rate of evaporation depends on the difference between the relative humidity at the water surface (100%) and the relative humidity of the air in contact with the water. The hot water will heat a very thin layer of air molecules next to the water, and this guarantees that the humidity of the air in contact with the water will be very very low (even if the relative humidity of the surrounding cold air is high). This is because the amount of water vapor corresponding to a given relative humidity increases very rapidly as temperature increases. Thus, there will be very rapid evaporation into the layer of heated air next to the water surface — so rapid that it looks instantaneous.

    Obviously cold water wouldn’t heat the surrounding air as much, so the effect would be smaller –though probably still pretty rapid.

  5. chadb says:

    I did the same thing about 3 hours north of Calgary about 2 weeks ago – pretty amazing to a Texas boy…

  6. Darron says:

    Being an old thermodynamics guy, It takes heat transfer to cause the "phase change" because the heated water has a higher "delta T" than the cooler water, the phase change happens at a much quicker rate. Actually, Vaporizing isn’t accurate. It freezes in very small chunks. I could go on and on… It’s just cool to know it works.

  7. FB2 says:

    I’ve spent some months in Fargo, luckily in spring time. Man, I hope you chose some different hot water source for your experiment than my first thought. It’s not something you should do in Freezing Fargo.

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