Why -20 to 50 °C?

There are many places on Earth which get colder or hotter than this...
Yes but are they extensivley inhabitted?

Maybe not where you live, but where I grew up -40c happened nominally several times per winter, and I pity the poor Canadians that suffered worse in Manitoba, and all points north of there. How about Siberia, and northern Europe.

These all have a pretty good population base.

But true, statistically, this covers most of the tropical range. As well you get more expanded range on a linear scale if you limit it to this.

About 20 years ago I spent a week near Jackman, Maine, at a hunting cabin. When I arrived I noticed soot on the undersides of the fuel-oil tanks outside the cabins. I asked the proprietor about it. She told me it could get down to -60 F some nights and so they had to build fires under the tanks to melt the fuel-oil lest the cabins - and their occupants - freeze to death. It didn't get that cold when I was there, thankfully. All we got was one badass blizzard that began about 20 minutes after I arrived.

And knowing the exact temperature would have helped how?

Why? Are you competing with AP#3 for the D'oh Prize?

Did I say anywhere in my post that I needed to know the temperature or was I just relating a similar experience to the poster above?

Why would you want to live anywhere that is <-20 or >+50? D'oh!

You know, maybe there are few billion people - like seven billion of 'em, with you as the sole exception - who didn't have a choice where they were born? It just so happened that some of 'em were born in places that get exceptionally hot or cold? Well, waddayaknow!

Damn, what a stupid question, d'oh.

Think about it. Anything outside this range would be wasted on humans.

Why have a thermometer that goes from -60 to +150° C when no one could survive at those temperature extremes.

There are, obviously many thermometers that DO go outside that range on one side or the other, or both.

How hot does your oven get? How do you know?

This doesn't address your question, but from where did you get that table?

For example, autoignition temp of kerosene is 220°C, boiling point of Hg is 357°C.

266. Mercury Thermometers
Through the development of special glasses having high melting-points it has become possible to construct mercury-in-glass thermometers reading to 550°C. or even higher. In such high-range thermometers the space above the mercury column must be filled with a gas (usually carbon dioxide or nitrogen) at a final pressure of about 19 atmospheres, in order to keep the mercury from boiling. For such thermometers the properties of the glass are of the greatest importance, and the glass known as "Jena 59III" is the best one to use. Even with this glass if the thermometer is kept at 550°C. for an hour or more a permanent expansion of the bulb will result; this will permanently lower the freezing-point reading, but if this change is applied as a correction (added) to subsequent readings of the thermometer, fairly correct results can be obtained. Thermometers of mercury in clear fused quartz have also recently been satisfactorily constructed for use up to about 700°C.

From: A. Wilmer Duff. A Text-Book of Physics 5th ed. P. Blakiston's Son & Co. Philadelphia (1921) pp. 207-208

A Mercury Separation in Your Thermometer?

Liquid-in-Glass Thermometer

Thermometry (PDF)

Thermometer filling liquids (PDF)

An Experimental Study of the Absolute Temperature Scale. IV. The Reproducibility of the Mercury Boiling Point. The Effect of Pressure on the Mercury Boiling Point

Thermodynamic temperature

History of the Celsius temperature scale

Anders Celsius (1701-1744)

Daniel Gabriel Fahrenheit

Fahrenheit temperature scale

Triple point

Mercury (element)

Why is mercury a liquid at STP?

Why Is Mercury Liquid (Or, Why Do Relativistic Effects Not Get Into Chemistry Textbooks) (PDF)

Correlation for the Vapor Pressure of Mercury (PDF)

Heck, I bet they have 'em BIGGER in Texas
Del

Dang straight!

-A-

Presumably that's about 3' tall
Del

Yep standard Texas belt buckle size.

Let me have a guess: its the expected range of room temperature! Besides you saying its garden variety nothing else maybe suggests its meant to be used outside.

Reading the OP's post and the responses from my learned friends I believe that the obvious answer has been overlooked - the majority of 'liquid in glass' thermometers are in the -20 to +50 range for one simple reason: this is the most popular range demanded by the market!

This range means that for the majority of applications (like room temperature for example) the temperature would be mid-scale and easy to read. Manufacturers response to market requirement.

For those with more demanding requirements, thermometers of different lengths, different scales, different graduations and different liquids are readily available.

If your requirement is for a specific range or calibration then I doubt whether you will find this in your 'common garden variety' hardware shop but would have to visit a specialist thermometer supplier.

Hope this helps to address the OP's query!

Hi Guys,

Back in the 1969 & 1970 I saw -65F twice. (no wind)

Once in Geralton Ontario and once in Moosonee. (James Bay)

I worked for Transport Canada serving the airport navigation

systems in all of Northern Ontario.

I was trying to start the Ford Ranch Station Wagon and it did start.

It barely crank over even it had been plugged in all night

But when I drove it to the LF Beacon in Nakina the wheels

felt they were square for a couple of miles.

I also did some maintenance for Weather-Canada at the same time,

so we knew the true temperature.

In Mosoonee nothing started except it was inside hangars

What a change in the weather during the last 50 years. ?

It feels like summer all year round Ha, Ha. But we still got lot of snow this winter.

And the coldest was -32C this winter where I live. (Sudbury)

TTYL Jens

Supply and demand on a local basis.

Here's mine...I live in Maine and I also have a digital one with an outdoor and indoor sensor. I'm pretty sure I would not want to experience any of the extreme ranges it's capable of.

As you say, "garden variety"; that's the temperature range encountered in the area where the thermometer is to be found. If you lived in Manitoba, the thermometers would reflect their temperature range.