We’ve had a bit of a cold snap here in New England, and recently the temperature dipped below 0º Fahrenheit for about 24 hours or so. I have a Chieftain non-tunable whistle that I usually keep in the car, for busking and the odd tune while waiting around. Normally, the bell note is pretty much spot-on Bb. But I played a few notes on a lark last night, and found that I was now the proud owner of an A whistle! At least until it warmed up…
So they ARE tunable after all. 
Try-out the carbon dioxide belch ‘method’.
Bob
Ooh… I like an ‘A’… but I’m not going to stand around in minus Farenheight with a Bb whistle – I’ll stick to buying the 'A’s.
So wait it got LOWER in pitch when it got cold?
Shouldn’t it have gone up to B or C? I’m just thinking metals contract in the cold and expand in the heat, so it should have gotten shorter and narrower.
either way below zero f is no joke!
If metals like aluminium expanded and contracted that much over relatively small temperature ranges, then modern life would be impossible. A Bb whistle contracting to a B or a C is not a goer.
It’s to do with air temperature and the speed of sound. The speed of sound is lower at lower temperatures, and the pitch will drop. The air in the whistle is more dense (the particles are moving slower) at lower temperatures meaning that it takes more energy to move its mass. At higher temperatures there is less mass and the pitch rises. Aluminium conducts heat well, so it takes a little while to warm up the air column properly.
All wind instruments go flatter in the cold AFAIK.
Yes shorter is sharper, but narrower is flatter (more impedence from a narrower bore).
If the metal contracts the same in all directions, that amount of contraction is a far larger percentage of the bore ID than it is of bore length (around 24 times greater, I think).
My understanding is that the contraction/expansion of the metal is an almost insignificant factor and that the temperature of the air column is by far the most important factor, as described by ecadre above.
Expansion and contraction is proportionate, so so the ratio of length to width will stay the same.
As benhall says, the contraction/expansion of the metal compared to the temperature of the air column is insignificant.
This page gives the calculation for the linear expansion of a 2700 millimetre bar of aluminium from -20 to +30 degrees centigrade. It’s 3mm.
https://www.alumeco.com/knowledge-technique/general/thermal-expansion
Incidentally, I noticed that the thermal expansion coefficient of ABS plastic is around 4 to 5 times that of brass, which is probably the real reason that dipping the head of Generation and other similar cheap whistles in hot water helps in removing the ABS plastic head.
I decided to do a little search on the matter, and if you don’t believe me, how about a Professor of Physics at the University of Virginia 
http://www.physicscentral.com/experiment/askaphysicist/physics-answer.cfm?uid=20080506014548
Very interesting article by the UVA professor. It never occurred to me that much air action took place inside a flute; it’s invisible but we hear the effects. My aluminum whistles (Anak) have hardwood heads and aluminum bodies, so there must be some interesting wood + aluminum voodoo going on there. If I’m compelled to play outdoors in near 0 degree F conditions, I think I’ll pull out my Susatos.