Deciding whether to leave them out tonight or not...

http://www.springerlink.com/content/j314qn1314271742/
http://www.actahort.org/books/174/174_25.htm
http://www.lpl.arizona.edu/~bcohen/cucumbers/greenhouse.html#grow
http://www.springerlink.com/content/l68581673720u024/

Conclusion: for a little while is OK, but not if the whole
night is cold. 56F low one night (5/7/08) was OK, but I'm
taking them in for this 41F expected low.