Okay, it must be spring.
I can tell because, after installing Mike's front fenders last week, I found myself biking to work in the rain on Monday. It was pouring, actually, and had been all night. So I was all kitted up - in the rain pants, the boot covers, the bright red rain jacket. (I'm so glad I chose the bright red jacket, incidentally, when I was shopping for it. I could have bought the black one. But the bright red is just so much more happy to pull on when it's grey and rainy outside. Not to mention I feel invisible enough in the rain without wearing dark colours.) And I was okay. Warm enough, once I got moving. And the fender performed admirably - such a difference when you don't have to worry about water being thrown up into your face.
But the moment when I knew it was spring? That was when I was nearly to work, and I actually steered at a puddle at the side of the road, sending a cascade of water up into the air (but not into my face) and over my rain-pant-clad legs.
It was damn satisfying.