I think it also depends on local habits - here in the UK, it’s quite common for the girls to wear brand new winter coats and boots back to school, which happens in the first week of September, so even if it’s still pretty warm, everybody else then feels comfortable to get their own boots out of the wardrobe by mid-September.
My guideline is layering: if it’s cold enough to wear two layers: T-shirt and shirt or camisole and cardigan, then it’s okay to wear boots!
K
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