Pansies grow in a wide range of temperatures. Most are killed at approximately minus 5 degrees Fahrenheit. They stop blooming in the heat of late spring or early summer.
In areas with extremely cold winters, plant in spring as soon as the soil thaws and is workable. In mild climates, pansies are best planted before the first frost, but can be planted until the first hard freeze, when the soil can no longer be dug.
Fall-planted pansies in mild climates can bloom from fall through spring. During the coldest part of winter, they curl up and rest. During winter warm spells, they open up and bloom, then start to bloom full-time when the temperature warms up in late winter.