Only about 10% of earths population live in the southern hemisphere. It’s pretty fair to assume northern.

Maybe, but if you're trying to appear folksy by using region-dependent seasonal identifiers rather than, you know, dates AND you're happy that instantly means 10% of your readers will be confounded by that, then I guess go for it.

I'll note that about 40% of the earth's population lives in the tropics, where seasons also don't break down the same way they do for the author - typically that demographic will recognise two identifiable seasons through the year.

What's the confusion here? The author is from Sweden, also neither I nor the author are North Americans.

While one half of the planet is having spring, the other half is having autumn.

Yeah that's something you generally learn when you are a kid.

We should catch up next autumn for a quiet ale to talk about the ambiguity of that date format.