The first version of this is live.
Click Options → Weather on the calendar page and add locations for forecasts:
If you enable more than one they get names on the calendar:
Click for a more detailed view:
Note that I am going to have to swap out the hour data for 3 hourly. I got a bit caught out by the sneaky pricing page on the providers site (10m calls/month only allows 2000 calls/day to the API endpoint that gives hourly data … grump grump).
Thought that I might as well release what I have so far to get the bugs out ahead of a Tweet etc…
Update 7th April 2020: The “wind” info now links to Windy.com.