Like neuro, the 5d II is equivalent if not maybe a hair better sealed than the 50D/60D... The 7D i have been able to shoot well in a snow storm or two and haven't thought twice about shooting in light rain (even though I made sure to get it in dry conditions as soon as possible after shooting... The 5d II being like the xxD series, I've had my xxd cameras fail on me when shooting in high heat and high humidity... (no rain)... They would cease functioning until I got them in a dry A/C room to cool and dry off. I dont think it would be as bad if you were shooting with sealed L lenses... (less rain to get into the internals and sensor) but still it's taking your chances... As a bit of very cheap insurance, carry a spare plastic grocery bag with you... when needed, rip a hole in it, slide the very end of the lens through the hole, bonus if you have a rubber band to seal the bag, and shoot until you're done... Dont overstay your welcome and get dry ASAP but if a freak raincloud pops up you're covered.