Trans Mongolian jan - march bad time too go?!?

Hello,

Ive been wanting to travel overland to asia and want to take the trans mongolian express for years. I was planning to go May 2008 time which I beleive was a good time to go 'weather' wise, however my life has been turned up side down and I need to get away asap!! I would like to spend 3 weeks travelling up through eastern europe to St peters, then take the trans mongolian express. I plan to leave early 2008 (Say maybe jan 1st), so Id take the trans mongolian express some time between end of Januray and end of feb. If this a good time to go?!?!? or would I be better to wait 1 or 2 months, if I can handle living here?!? advise please...