According to the October, 1919 issue of Good Housekeeping, October is the last fresh vegetable month:
The Last Fresh Vegetable Month
In October vegetables may still hold the post of honor on the table which is planned on a truly economical and sensible basis. By using freely and consistently what is in season, and by utilizing especially the delicious vegetable overflow, it is possible to lessen the meat bill appreciably. If we do use the abundant fresh vegetables lavishly when in season, it will make us feel more comfortable about the increased meat consumption, which the cold weather later makes necessary. The savings on meat and grocery bills when we effect by living largely on vegetables during the summer and fall will help us to balance the budget satisfactorily.
A hundred-years-ago people apparently ate more meat in the winter than during the warmer months. I don’t think that my meat consumption varies much across the year, though I have vague childhood memories of having strawberry shortcake as the main course sometimes in June, and being told that, “We eat lighter in the summer because it’s hot.”