Cold Resistance 2 is a Tier 2 ability. It makes a plague evolve even more resistance to cold climates, and is invaluable in speeding up infection spread in cold climates, especially Greenland and Canada. It is the opposite of Heat Resistance 2, though both are required under normal circumstances to unlock Environmental Hardening.
In the Frozen Virus scenario, you have it at the start. It can't be devolved.
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