During cold spells, it is not uncommon for ice to build up in gutters and downspouts, but with proper maintenance, you can limit the severity. Excessive ice buildup can lead to leaks caused by ice damming, which is not warrantable.
To prevent ice accumulation, keep gutters and downspouts clean and unobstructed by tree limbs, leaves, balls, trash, etc. If you encounter ice damming, consult a professional for help.
More information is available here: Preventive Maintenance Plan for Ice Damming.