Pansies do best when its over 40 degrees, everything will freeze at 32 degrees so if you put pansies out during the daytime, bring them in or cover them at night so they don't get a hard frost or freeze. I've seen them survive a light snowfall but you should protect them.
At what temperature do pansies freeze?
In my area (zone 8 temps fall to 10°F) pansies are considered winter hardy. However, the low temp occurs just before sunrise, and is not usually sustained. Right now I have pansies planted in clay pots on my back deck. We have had 28° temps for two days with sleet and freezing rain. This will cause some damage, but I fully expect them to recover when this cold passes.
We plant them in late fall, and they remain low to the ground over the winter. They start blooming in early spring, continuing until it gets too hot for them.