A seasonality effect is a recurring change associated with a time of year. For product sales, compare category-by-region heatmaps from different periods: a peak in one period may signal demand worth planning for. section 4.2
A summer demand question
Suppose air conditioning units and beachwear sell more strongly during summer in warmer regions. Compare heatmaps from other times of year before treating the peak as seasonal. Weather is a plausible explanation, not a cause established by the heatmap alone. section 4.2
Turn the observation into a decision without overclaiming:
- Compare the same categories and regions across times of year; also look for peaks associated with holidays or the academic calendar. section 4.2
- Use a credible pattern to inform inventory and promotions, while checking whether it reflects a recurring shift rather than a new market trend. section 4.2
- Be cautious with correlations between time series: shared trends, seasonality, autocorrelation, or external shocks can make a relationship look stronger than it is. section 2.6.3
