Your plants should be fine. I'm assuming your plants will be getting full sun and the soil conditions are better than mud. Do you know which cool hardy ones you purchased? I would only worry if temps stayed in the 50's or even low 60's with very wet conditions (incessant rainfall). You are right in assuming that hardiness increases once the corms start to leaf out and the plant establishes itself. My current inventory of cool bananas includes Himalayan, Chinese, Basjoo, and a few dwarfs. PS., Something you might consider for the future is to plant the corms first in a container and letting them get established before transplanting into the ground. This way you get to more directly control temperatures and moisture conditions. Good luck!

Thanks very much for the reply. They are in a location close to a south wall and get all day sun. I got FHIA1 (Gold finger) and FHIA 3. Here is what they say in the catalog:

GOLDFINGER (FHIA-1) - A rapid growing, mostly green plant producing a wonderful tasting, slightly sub-acid, refreshing fruit that gets 6-8 inches long or better. It is a very disease resistant, wind & cool tolerant plant that is easy to grow. In our area the ripening fruit does not get dark yellow, instead gives only a slight color change when mature so check it often when close to harvesting. Height 10-12 ft. This one is a MUST.

FHIA-03 - Another strong plant, specially bread for hardiness. The fruit is firm and refreshing with a hint of lemon. Can be cooked green or eaten fresh when fully ripe. Delicious! Grows about 12 feet tall with stout pseudostem.

Thanks!