Frost was last night (4/30) - down into the high 20's in some areas. Should not be a problem for any perennials - they are frost hardy plants - although foliage not yet hardened off may experience a bit of damage but the plants themselves should be fine. Annuals are another matter - depends on what you have. Some cool weather annuals can take light frosts without worry (if hardened off) and others will be toast - impatiens, coleus, tomatoes, peppers, etc.

Thanks God , I am glad that it is over for those affected. In my Area it got down to abot 36F. All I had out was cool crops, nothing to worry.
Now we are having georgeous weather around Seattle aread. I hope you have to.
Happy Gardening to all.

31.6F here in the foothills east of Renton. No noticeable damage.
Mike

My car developed a nice layer of frost on the windshield, but all of my tender annuals(I planted pumpkins out last weekend) seem to be fine. :)