After I build a performance engine, I would break in the camshaft and lifters per mfg. suggestions. The ring will seat after it runs some. If the cam is used then I usually break them in at the drag strip. If it is going to break then it is going to break ( note I do use racing bearings with a grove in them and I have a lot of clearence ) What I call a performance engine and what you call one might be diffrient. I would not think cold weather would effect the breakin, it would just be harder to get the engine warm.
I usually crank mine up, idle it up to keep it running, set the timming with a light or ear to keep it running then idle it up around 1000 - 1500 rpm let it reach operating temp. Checking oil pressure, temp, listen to engine, checking for oil leaks etc. The I would turn it up some, then to the drag strip or Dyno I go.
Hope this helps......
John