How do I forecast seasonal products?

Separate the seasonal shape from the underlying trend. Work out the index for each period from prior years — what share of annual volume falls in each week or month — then apply this year’s expected total to that shape. Adjust for calendar shifts, since holidays move and a week-numbered comparison can misalign them.

Seasonal buying is dominated by lead time. If the peak is in November and the lead time is sixteen weeks, the decision is made in July on partial information, and the reorder window has usually closed before the season proves the forecast.

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