What will the weather be like?

On the way to answering this question I looked at the pilot charts for the relavant areas.

I have included charts from June through October as these include data for the approach to and departure from the passage itself.

Pilot Charts

Pilot charts are built from historical data, primarily ship's reports. Therefore, there is no data where the waters are not typically navigable. There is data at the east and west ends of the passage but nothing for the center. I presume from the information that I have that the conditions are not generally colder or rougher in the middle of the passase than they are at either ends

North Atlantic

These are 3-page pdf files. The best view of Greenland and Baffin Bay is on page 2.

June

July

August

September

October

North Pacific

These are single-page pdf files.

June

July

August

September

October

Notes

Pilot charts are a good source of information on average wind and sea conditions. Specific conditions may be substantially different.

Notes on how to read pilot charts are included on the charts themselves.

The complete set of pilot charts of the world is available through the Atlas of Pilot Charts