Are mercenaries effected by Temperature scales?

[Norfleet]

Units do not have temperature preferences. Racial temperature preference is strictly an economic-only behavior. All units, regardless of their race, suffer +2 encumberance in Cold-3 and Heat-3, respectively, and no penalty in Cold-2 and Heat-2. This is negated if the unit has Cold or Fire Resistance for Cold and Heat, respectively.

UNITS HAVE NO TEMPERATURE PREFERENCE.

This is tested: A Return of the Raptors Caelum Raven Guard, which has no cold resistance, suffers the +2 Severe Cold encumberance penalty when fighting in the cold-3 of Caelum. A regular white-wing Caelian unit with Cold immunity suffers no penalty, not because it is a Caelum unit, but because it is cold resistant! The only other exception is a Cold Blooded unit fighting in a Cold province, which I think is +1 encumberance for each cold scale in addition to the severe cold penalty (untested).

[Psitticine]

The only thing I'd add to that is that cold/heat scales will affect supply levels in a province based on the nation's own preferences, and supply level in turn applies to mercenaries stationed in the province.

That's not what the original poster is asking about, obviously, but I thought I'd point it out as being germane to the general topic of temperature and mercenaries.