You might argue that any change of course around bad weather is a weather diversion. I flew back from Sydney to London with a three days stopover at Bangkok and on both legs we made a significant detour off our track to avoid bad weather. It probably only added five minutes in each case but I am pleased that we did.
The route can vary significantly on long sectors reflecting jetstreams, overflying rights, congestion etc and bad weather will certainly be one factor. 90 minutes must be a record though.
In the case of New York - Singapore I suppose that it could even affect whether you fly over the Pacific or Atlantic.