A few facts:
1) A very cold battery will lose its charge quicker and so if you use a laptop on battery when it's cold you may have less runtime (NB: I am not talking about battery self-discharge)
Lots of info here: http://www.mpoweruk.com/performance.htm
2) You will often see condensation on items brought in from cold environments but this is not the only reason you let them warm up before switch on. The other reason for waiting is because switching on a cold item and letting it heat up rapidly may result in thermal shock to delicate components (eg: disk drives and LCD screens, especially the glassmount screen connectors) as their parts expand rapidly.
Hope this helps.
It's been 3 months and finally pin-pointed the problem. It's a hardware problem and that spammy-looking ad-filled Indian site was right (won't post it here as it's a commercial entity), it's chip-level damage that's common to a number of Vaio laptops.
So the best and probably the only solution is to turn it over to your nearest service center for repairs. If it's under warranty, you're fine. If not, well, expect shelling out a few bucks for it. You might be better off buying a new notebook.
Anyways, I got another workaround and it's highly dangerous. I am only sharing this for purposes of informing that there is a way to get around it, but has its tradeoffs. This is not sound advice, just stating that it's possible.
This dangerous move involves disabling the ACPI critical trip point of the Linux. To do this, one must edit their grub file:
gksudo leafpad /etc/default/grub
And add thermal.nocrt=-1 to GRUB_CMDLINE_LINUX_DEFAULT as shown:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash thermal.nocrt=1"
Then update grub:
sudo update-grub
Then reboot.
This disables the ACPI critical trip point but not the thermal sensor, so that we can still monitor if afterwards.
After doing so, I ran my logger script. However, to compensate for the lack of a natural trip point handler, I set GKrellM to fire an action when the event happens. Since GKrellM is usually delayed, it's good for knowing that when it goes over the trip point, it has gone over it for a significant amount of time when I fire an action.
Then I went on with my usual routine. After doing so, the system tripped it again. However, it was a sudden spike, that it did not even register in GKrellM but my logger got it recorded. It's a very abrupt spike and that was it.
Best Answer
The slowdown is caused due to the processor clocking down during boot-up to prevent overheating damage. Paradoxically, laptop CPUs are likely to overheat when booted at cold temperature due to the nature of the cooling assembly used in laptops.
Laptop CPU cooling assemblies usually consist of a flat plate positioned over the CPU and connected by a long copper heatpipe to a heatsink and fan off on the side of the case. Heatpipes contain liquid in a vacuum which provides cooling by capturing heat at the CPU end through vaporization and releasing it at the heatsink end through condensation. It is very likely that in cold temperature, the liquid within the heatpipe freezes and it no longer functions effectively for cooling the CPU until thawed. According to Wikipedia:
This would not happen in a desktop since the heatsink is in actual contact with the CPU and can thus absorb and dissipate heat in and of itself. However in laptops where the heatpipe critical for funnelling heat to the heatsink, it is quite possible for the CPU to overheat and become throttled while the heatpipe is warming to operational temperature.