Your cold spells are more powerful when you cast them in a cold region.
Prerequisites: Con 13, Snowcasting.
Benefit: In cold areas (temperature at or below 40° F), spells with the cold descriptor cast by you manifest at caster level +1.
In areas of extreme cold (below –20° F), cold spells cast by you manifest at caster level +2.
Source: Frostburn, page 48.