Good to hear you want to ride in the snow and now wait for the summer!!
On my 00rm125 i changed from 175 main and 50 pilot to 188, 45 and raised the needle two clips, that worked the best. However it didnt seem to be possible to make it work good when trail riding, it would pretty fast go rich, probably because of the cold air(-15 to -25!) cooling down the engine cause the pilot was actually leaner than in summer. Next year i willprobably install a termostate. Impossible to get the right operating temprature in my kind of riding.
I have always ridden year round. From +25 in the summer to -25 in the winter. Before i owned a 93cr250(damn i miss it wintertime) it had what i could see perfect jetting except a little rich on the low circuit. I always used the same, pretty cheap oil, 3 to 4%. Never needed to rejet it for the winter, worked great year around, always started and fan fine.
If your bike ran a little rich on summer then it might run good now. Use the same oil, depending on what kind of riding you do you may add more oil if you are lake riding, if you just play around it should be no problem running whatever ratio you use in summer.
Winter is over here and i cant wait to throw some dirt but the winter is just as fun!