Many pansies can tolerate temperatures to 5 degrees below zero Fahrenheit. It is best if they are planted in fall so they have time for their roots to become established before the first hard freeze.
During freezing conditions, pansies often curl up and look wilted. Even though frozen solid, they will perk up and bloom during warm spells in winter. They will resume blooming full time once warmer weather returns in late winter or early spring.
Pansies should be planted in moist, well-drained soil and mulched to prevent drying in winter winds. A slow-release, balanced fertilizer (such as 10-10-10) maximizes root growth and flowering. Watering during dry spells keeps tissues hydrated and less prone to winter damage.