I wanted the months to be equally-divisible into weeks of equal length. It turns out that the 7-day week is the only really good way to divide the year equally into smallish units and only have one or two days left over.
So you could have four season-months of 13 weeks (91 days) each. But I like the idea of months that are in the same ballpark as lunar cycles. Lunar cycles and solar cycles don't mesh, so you can't have months that perfectly match lunar cycles unless you're willing to have months that float against years the way weeks currently float against months, but then again some people might find that appealing.
So you could have four season-months of 13 weeks (91 days) each. But I like the idea of months that are in the same ballpark as lunar cycles. Lunar cycles and solar cycles don't mesh, so you can't have months that perfectly match lunar cycles unless you're willing to have months that float against years the way weeks currently float against months, but then again some people might find that appealing.