Hail Ants: “I recognize the obvious advantage of a metric (i.e. base ten) system of measurement.”
I disagree with that, though that’s probably for another thread.
“Put simply, when dealing with weather, on average, what’s the coldest it gets? Call that point A (or 0[sup]o[/sup] F). What’s the hottest? Call that point B (or 100[sup]o[/sup] F). Divide the two points by 100 units (hey, base ten!) and you’ve got the perfect system for measuring air temperature, the fahrenheit scale!”
I definitely agree with that. While there are some locations where about 100 degree temperatures are common and some where below 0 degree temperatures are common, these are the exceptions rather than the rules. Also, if you do encounter these exceptions, you know that it’s either really hot or really cold. The Celcius scale forces you to deal with negative numbers frequently during winter, which is a recipe for errors. Everyone who has ever done or corrected math homework knows that it is far easier to lose negative signs than to actually screw up the value of a number.
From Cecil’s Column:
This is written in a disparaging manner, but the desire to avoid negative numbers is a good one, and “colder than it ever gets in Denmark” is also colder than it ever gets where I live.
scr4: “In both systems, you need to use negative numbers once in the weather forecast once in a while, for most countries.”
I can’t remember the last time I experience temperatures greater than a hundred or below zero. However, I encountered a temperature below freezing just a few weeks ago. There’s a difference between “almost never” and “every winter”.
“We’re all familiar with ice water and boiling water, and they have well defined temperatures. Using these as standards doesn’t seem any more arbitrary than using ‘the coldest it gets’ and ‘the hottest it gets.’”
Call me crazy, but I think that human experience should be the basis for reporting things like what humans will experience (e.g. the weather), and that the experience of liquid water is somewhat tangential to that.
MrSleep: “Saying the word “celsius” sounds much more scientific than the word “fahrenheit.””
Here’s a rough outline I’ve had about this topic in the past.
Me: “The number ranges you use for weather reporting are more comfortable in Fahrenheit, and you rarely have to use negative numbers.”
Opponent: “Celcius is more scientific than Fahrenheit”
Me: “Kelvin is more scientific than Celcius, why don’t you use that?”
Opponent: “Because then you’d have to deal with ridiculously big numbers all the time!”
Me: “Oh, so which numbers you have to use and the relative convenience thereof is important to the choice of a measurement scale? The number ranges you use for weather reporting are more comfortable in Fahrenheit, and you rarely have to use negative numbers.”
Opponent: “But Celcius is more scientific!”
NanoByte: “For almost all everyday uses, you don’t need the F scale’s nearly twice-as-high resolution, and without that resolution, C avoids 3 digits almost all the time.”
In my book, that lousy negative sign you need to deal with all winter is far more annoying than an extra digit you sometimes need to use in some areas in the summer.
tbea925: “You are aware, I’m sure, that the metric system of weight (a gram) is defined on a cubic centimeter of water at 4 degrees C.”
So? There’s a corresponding Fahrenheit temperature for that as well. And besides, if this is such a critical temperature, why isn’t it the basis for the scale? Besides, the density of water doesn’t change all that much with temperature (until it freezes).
Arnold Winkelreid: “… the Centigrade (Celsius) scale is more widely used in the world”
[condescending mother voice]And if all the other countries jumped off a bridge, would you do it to?[/condescending mother voice] 
We’re constantly telling the nation’s children not to cave in to peer pressure. How can you possibly think that peer pressure is a compelling argument for anything. 
“In general terms, below 0°C the rain generally turns to snow and the puddles into Ice. This is a weather milestone and is very important if you’re talking about the convenience and usefulness and reasonableness in terms of the air temperature.”
This might be an argument for making the freezing point of water a nice round (easy to remember) number, but not for making it zero. A lot of other conditions contribute to this, anyway, though. The most important would be the temperature of the ground which is seldom reported anyway.
“Also, the scientific applications are obvious to anyone with (insert flame here).”
Nobody said scientists weren’t allowed to use Celcius. Furthermore, the scientific applications of the Kelvin scale are even more obvious, but we don’t see the world flocking to Lord Kelvin’s defense, now do we? Besides, scientists use a lot of things that I don’t need on a day to day basis. Most people use “mass” and “weight” interchangeably, but that would annoy some scientists. Why saddle the masses with scales that are inappropriate just because some scientists like to use a particular measurement scale for some applications?