other webcrawling reveals that highest-recorded wind gust speeds on sw tip of uk are over 80 knots in jan and decemebr, 70 mph in feb and march, dropping to 60mph from april.
I'm looking at the routing chart for December right now. It isn't the worst month for an eastwards crossing of the Atlantic, but the risk of a major storm (F10 or above) does grow in the north-west of the Atlantic, particularly north of 40N. That is true throughout October - March.
I don't think anyone can answer this for you. You need to look at these charts in the light of the route you might take, and decide what level of risk you are prepared to accept. If you don't have monthly routing charts for North Atlantic to hand, they can be viewed <A target="_blank" HREF=http://pollux.nss.nima.mil/pubs/pubs_j_apc_sections.html?rid=10499>HERE</A>.
I dont think you can plan to have "nice" weather for three weeks in the North Atlantic, maybe we've just been unlucky.
We left for Azores in May and Bermuda was hit with solid 45knots for days, so we stay'd East of them, then 300 miles SWish of the Azores, a trough came down to meet us, 45knots for 48 hours and a rather large sea, and we were worried about running out of wind! then from Azores to Spain, Southerly gales in July? we struggled to make the corner and decided against Bayona? I think on a passage of any more than 4 days, you'll probably get something interesting, as thats all the forcasting can manage. We have a whole list of winds blowing the 'wrong' way!
My girl friends flying back next time!