The ground cover plants and cannas can be covered to help prevent frost bite. I think that as long as the temperatures do not stay below freezing for too long you will be safe. Bring indoors any tender ferns or flats of plants you may have bought. It does not feel like it is 30 out, I think it is something like hail, some sort of convection current, I have never seen it snow and thunder and lightning at the same time. If you can't move them inside cover them with at least a double layer of burlap or a tarp.
Old blankets work great also.
The key is to keep the cover as close to the ground as possible to trap the natural heat from the ground.