Answer: Weather can be so variable in the spring! Daylilies are very tough and resiliant plants; I would expect them to have sufficient root reserves to overcome their initial tough time and grow well for you this summer. Make sure to keep them well watered and mulched and provide a bit of extra compost or possibly a light application of a complete granular fertilizer in accordance with the label instructions to help them along.
Next time you plant out new perennials, try to do it on a cloudy day or in the rain to minimize stress. Cover them with a bit of straw or old oak leaves or an upturned flower pot or cardboard box to protect them from extreme cold should it threaten at night. In the day, remove the pot or box to avoid overheating. It can also be helpful to shade them slightly (leaves or straw work fine) and protect them from drying winds for the first few days to allow the foliage a chance to green up gradually.
Once they are in the ground, keep the soil evenly moist but not soggy until they become well established. Using several inches of organic mulch around but not touching the plants can also be helpful in conserving moisture and keeping down weeds.
Enjoy your perennials!
Q&A Library Searching Tips