A medium plug is good all year 'round on most engines, I'd run the lc4.
As for the hot plug in cold weather, it's the other way around....But like I said, a medium works in most applications.
If you have the famed "chewbacca" idle, chances are the lsn is about 1 turn too lean and/or you have the leaky carb that Piccos were known for. I'm pretty sure Picco has addressed that problem by now. The chewbacca idle comes in handy on some engines because it absolutely means the low end is lean, whether it be tuning, air leak, or both.
My picco is running quite a bit less than 1mm, it's more like .5 or .6mm.