Just for fun:
"...
We picked up the 15 most-sold mobile phones in Finland and three others for comparison, and took them into the Technical Research Centre of Finland and their "Weather Room", a specialized research lab where the temperature can be adjusted to a fraction of a degree.
...
Failing First: iPhone 4S

At 0 degrees Celsius / 32degrees F, it was business as usual. At -5degrees C/23degrees F, iPhone 4S and Nokia N9 started showing symptoms: the iPhone reported a sim card error and the N9 claimed its battery was nearly empty.
...
Out of the 18 phones we tested, only two feature phones could survive until these temperatures: a very cheap Nokia C1-01 and a five-year-old Nokia E65, which was one of the devices chosen for comparison. In the end, the Finnish engineers did design the best mobile phones for sub-zero environments. They may not be equipped with high-end touch-screens, but they work! And it's probably not a surprise: the coldest temperature in Finland peaks at -40 degrees almost every winter.
..."
http://www.macworld.co.uk/ipad-iphon...pe=allchandate

Maybe it is time to test my N900. ;-)

@PMaff,

I can report that the N900 works fine at -20°C (e.g. this morning .

(almost) dito, -17 here.

N9 works fine with -10°C, I've just used it to take ice pictures yesterday, without any trouble...

Mine worked on -12°C without any simptones...

I don't think that the temperature of the phone changes during the time it takes to take pictures.
I've used the N900 in very harsh conditions, but I'm not sure it would still work after staying one hour in -20C.

N900 works fine with -20 degrees Celcius

Overclock it?

"Against all odds, South Korean Samsung smart phones outlasted Finnish Nokia's touch-screen devices. Only one of the smart phones we tested kept running smoothly when the temperature reached -30 degrees C / -22degrees F, and it was a Samsung."

Just cut the angle you want, and you get a different emotion from said article.

Moreover, common sense indicates that this theoretical exercise only matters if you're a coat-less smartphone-toting wild bear.

And even if that's the case, you should stop playing with your smartphone outdoors and go hibernate.