Are we like daffodils?

In the UK Sunday Telegraph this week there was an article that suggested that the emergence of flowers like daffodils was dependent on the number of days where the temperatures exceeded a given level (Growing Degree Days) - I think the article suggested it was 6 degrees C. For daffodils the figure was 50 positive days +/- 10. Negative days don't count as there is no such thing as negative plant growth. This allows you to predict with some certainty when the daffodils will appear in any given area.

I wonder if a similar principle could be applied to consumer behaviour with regard to purchasing spring/summer ranges. It would be interesting to test the theory. I suppose that the problem would be that a:) weather is local and b:) long range weather forecasts are pretty unreliable.