Signs of Spring

[multigeek]

I've never liked the modern definition of the seasons. Tying seasons to the solstices and equinoxes doesn't really make a lot of sense to me. So I ask this question: If there were no rule as to when spring begins, how would you know that spring has begun? What is different about the first day of spring from the last day of winter?

I have some ideas, and I'll post them later, so as not to bias any responses.