Some folks mist their trees to create a layer of insulating ice on the blooms. I've never done it myself, but have been assured it works. I think it will all depend upon their location and how sheltered they are. There is a frost predicted for St. Louis tonight, but my fruit trees are in such a location that only a very few blooms would possibly be affected. If your trees have any kind of sheltering you should be ok. I have 11 fruit trees in my back yard and didn't loose much at all in the April freeze last year. One or two nights shouldn't do much harm though if you aren't as sheltered. I do know that I run about a zone warmer here than central Illinois.
Another trick the orchards do is tend a fire near the trees on the night of the frost. I'm not too fond of that since I hate being up late and my local fire department isn't fond of back yard fires in such an urban area.
I did notice this morning that Macoupin Co is in a freeze predicted area according to one of the St Louis news stations. I don't know where you are in relation to that, but it might be worth investigating the mist proceedure on the net.