It took me a while to realise that the Y-axis labels on the “Monkeys Wedding” chart (who comes up with those names??) designated wind, not rain (which has been far more relevant here in Eastern Australia than anything else, and which is the main object of the chart, given that wind is more thoroughly covered in the “Sailor’s Delight” one).
How about using both sides for Y axes, matching font colour to line/area colour (as @wabu suggested 3 years ago)?
The names are related to weather. Monkeys Wedding, for example, is the term used to describe a absolutely cloudless sky in some countries. I used generic terms so that if you edit the graph, the name does not get misleading. For example, if I called it the “Rain” graph and you turned off the rain, the “Rain” name would be wrong.
It is difficult to find a balance between simplicity and helpful guides. For example, if I labelled the axis “Wind”, this will add clutter to the graph but after a few days, the label becomes useless because you know that it’s the wind axis now. If I had my way, I would remove many things, like the icons in the top right of the graphs.
You can edit the graph and add the second axis.
Doesn’t work, especially for areas because if the area overlaps the axis, you cannot see the numbers because they are the same color.
Sure, I can do many cool tricks like inverting the colour if the area overlaps or having help tips (e.g., axis labels) that fade over time (both of which are on the todo list), but it’s all about time and priorities.
Sorry, didn’t mean to question your design decisions 
I was just curious…
That’s cool! Except… I’m a cheapo free user 
(bc I don’t need the premium data sources and longer range forecasts).
I didn’t think you were question my design decision. I was just answering your curiosity. It also helps when people understand how we come to decisions.