Hi Shannon,

If your perennials were outside at the nursery (in other words, hardened there), you should be fine.  They also will have done some hardening this week in the ground; though we are definitely expecting a dramatic temperature change! 

Most perennials will be able to take this in stride.  If they have flowers, or flower buds, you might want to cover them since we are predicted to drop below freezing on Friday and Saturday nights --you could use sheets, frost cloth, or an upside down bucket or nursery container.  Snow cover, if we get snow, will also help protect plants from freeze damage.

I hope this is helpful.

Cordially,

John