Another good free resource to look at in considering the time & route you want to travel are the US Pilot Charts
which you can dowload from www.nga.mil
. Note they are a few megabytes for each month, so a broadband
connection is useful.
Go to the site and look under Publications, then (by memory) use the different pull down menus > Atlas of Pilot Charts
, > North Atlantic, > month required. Pilot charts tell you typical wind
strengths & direction, wave heights, sea temperatures, etc.
Good stuff in understanding why people say travel particular routes and times. (Look at the key on each chart to understand the code ...)