I heard it explained once, and it was complicated. I can't remember the explanation.
Here's one I Googled:
Fahrenheit may be the best way to measure temperature after all. Why? Because most of us only care about air temperature, not water temperature.
Think about it. When was the last time you used a thermometer to measure water temperature? It was probably in a high school or college class. If you’re ever in need of boiling water (e.g., when it’s time to cook pasta), then you can usually determine that the water is boiling by just looking at it. The steam and bubbles are a dead giveaway.
However, things are a little more complicated when it comes to measuring ambient temperature. You’ve probably browsed over to Weather Underground recently to see if you should wear a coat when you go outside. This is the only time most of us non-scientific folks care about temperature.
Celsius is great for measuring the temperature of water. However, we’re human beings who live on dry ground. As a result, it’s best to use a temperature gauge that’s suited to the air, as opposed to one that’s best used for water.
This is one reason Fahrenheit is superior
Fahrenheit is also more precise. The ambient temperature on most of the inhabited world ranges from -20 degrees Fahrenheit to 110 degrees Fahrenheit — a 130-degree range. On the Celsius scale, that range is from -28.8 degrees to 43.3 degrees — a 72.1-degree range. This means that you can get a more exact measurement of the air temperature using Fahrenheit because it uses almost twice the scale.
A precise reading of temperature is important to us because just a little variation can result in a perceivable level of discomfort. Most of us are easily affected by even slight changes in the thermometer, and the Fahrenheit scale is more sensitive to those changes.
And let’s face it: with so many home heating and cooling methods and technologies available, there’s already enough guesswork involved in keeping our homes comfortable. According to Foster Fuels, for example, homeowners who rely on oil heating already have to contend with a +/- 10% margin of error when reading their fuel gauge. And when every drop of fuel oil counts against that gauge reading, using a temperature scale with a higher degree of accuracy is extremely important when programming your thermostat.