This sounds like a job for better post processing. What focal length/aperture do you shoot at, and how many frames do you collect? What is your target - Milky Way widefield? I am guessing you aren't doing fainter nebulae, what with 30 sec anticipated exposure. What is your workflow? What is your astro processing program and which algorithm do you use ? Do you use darks series taken at the same temperature, or hot pixel maps, or whatever for subtracting the noise from your series of lights frames?
I have seen good wide-field astro-landscape images taken in 30 degree C conditions (summer in Missouri) using a 5D2. I am not very sophisticated about post processing, I am stumbling my way through Nebulosity, which is considered an easy to use astro image processing program.
The Cloudy Nights astrophotography fora are good sources of information about post-processing algorithms. The people who use home-built Peltier cooler boxes for their SLRs are generally chasing faint objects requiring a big stack of 1 to 5 minute exposures. Milky Way shots should be taken at ambient, and the camera stored at ambient before use.
Clear skies to you!