Runs warm in cold weather

[hksdrift240]

I've got a 95 nissan 240 with a mishimoto aluminum radiator, and recently when its like 20-30 degrees, the engine wants to run really warm. On days when its about 50 degrees, the temp will stay pretty steady at 193 degrees. When ever it gets to around 20-30 degrees outside, the temp will slowly go up to 210-220 before dropping back down to around 197, and then repeat the cycle. Whenever I feel the lower radiator hose, its ice cold. On days it was 60-70 degrees, it would run 185-190 degrees. I haven't done anything to this car in about a month now, so there shouldn't be air in the system...i had it tested a while back for exhaust gas in the coolant, and it was fine. I did drill about a 1/8 inch hole in the thermostat housing about a month ago. Any ideas as to whats going on? It seems that the radiator is overcooling the water, but i'd like to get this resolved.