If you are looking for something that will reside outside (sounds like you are), I would be looking for a "self-contained" environment. Essentially, you want your rack to be a data center all rolled into one economical unit. There is an interesting article "AOL Micro Data Center", that describes something similar to this idea. Your rack would live outdoors, and react to the changes in it's environment.
I would also check with your equipment manufacturer on the recommended operating conditions.
You don't want to void any warranties or put yourself in an unsupported configuration.
If you are talking about a rack in a building that is in those conditions, you would want the building to contain a designated area "server room" for the rack. The server room should have its humidity/ temp monitored and controlled.