A cooled camera is your best option - almost essential in hot weather.
I have a centalds cooled 60d. They are a very good company to deal with, but if you have a problem with the camera they may be the only ones who can fix it, due to the modifications.
Camera Clinic in Collingwood do astro modifications - but they are expensive.
I think the cheapest mod option (from what I have seen on other threads) is Peter Tan in Hong Kong -
www.tan14.com
I haven't dealt with him but the comments I have seen have been positive.
Regards,
Tony.