You can research your expected weather (long range) by studying the appropriate Atlas of Pilot Charts for the ocean(s) you will cruise.
Pilot charts depict in some detail the prevailing weather patterns including: wind directions and speeds, wave heights, ocean currents, visibility, barometric pressures, sea surface temperatures, and ice limits to be found in the areas covered for each month of the year.
Pilot charts are issued in 5 volumes: North Atlantic Ocean, South Atlantic Ocean, North Pacific Ocean, South Pacific Ocean, and the Indian Ocean. All information is presented graphically for each 5° section of the chart and describes the averages from meteorological and oceanographic observations made over hundreds of years for each month of the year.
Some can be obtained online for free download or you can purchase these at a chart store. If you study these, you'll know more about the probabilities of having appropriate weather and sea conditions for your passage during the time of your passage.
In your case, you'll pick up Pub 108 North Pacific Ocean.
An additional reference for any cruiser would be Cornell's World Cruising Routes
Some general information about the places you may visit and the seasons when you might not wish to be sailing--the pilot charts and Cornells' book will help you there. Also, check out your countries of interest in Noonsite
Would you enjoy seeing the Philippines? If so, you must be aware that the PI have a tropical climate with the rainy SW monsoon season from June to September, the dry season October to May. There is a high incidence of typhoons, most frequent between June and October. The best season for cruising is from early January to early May.
From there--more to the North and Japan? or Northeast and the Northern Marianas? I hate to admit it--but it looks like everything is an upwind battle leaving the South China Sea. I've visited the area flying in and out when I lived in Japan--not making my way North with a sailboat though. I am hopeful that another member will come along to be more helpful with specifics for you.
Once in Japan or even the NMI, you'll be able to take advantage of the natural circulation of the winds and ocean currents to get you over top the Pacific High (which moves around) and to bring you to North America along the Canadian coastline easily.
Several folks I know who live in Alaska and BC are talking now about the timeline of debris from the big Japanese Tsunami making way across the North Pacific. This is a new hazard--besides the normal weather windows that you will need to keep up on as you make your way to Canada. Depending on the size of the debris it is expected to still be on the ocean for many years though several researchers have noted that the debris is moving much more quickly than expected by the models.
One Tsunami debris video
Japan Tsunami Debris Tracked Across Pacific Ocean - YouTube