Only focusing on the 5 piece bonuses.
Hypothermia:
Applying the Chilled status also applies Major Defile to enemies for 6 seconds.
Enemies affected by Major Defile take 30% more damage from Chilled.
Hoarfrost:
Applying Chilled coats your target in freezing ice. Causing them to take X Frost Damage over 10 seconds. This can stack up to 3 times.
Whiteout:
Increases the duration of your Frost skills by 6 seconds. Adds an additional 2 meters to your Frost area of effect skills.
Death Chill:
Your Critical Chance is reduced by 100%. Your Frost damage over time effects have 1% chance to deal 1000% additional damage.