While the weather is not to cold and the soil not too hard, this is the ideal month to dig up your perennials, separate the roots, and replant them.
The ideal time to divide them is in the spring or in early fall before the nights become cool, and when the soil is warmer than the air for the better part of 24 hours.
To move a perennial with the least amount of root damage, begin digging at its drip line. The roots extend that far, so digging there lets you remove the plant with the majority of the roots attached. If they have fibrous roots (the kind that looks like hair), just pull them apart. If they have a thick root, simply cut it with a knife, but make sure you have buds on each side.
Not only does dividing perennials keep the plants healthy, but it is a good way to make more plants. The only problem now that you have twice as many plants is finding new spots to plant them. If you cannot plant them all, give some to friends and neighbors.