Since we live in the wine country, we know all too well that Mother Nature always laughs last. You can plan all you want, but the weather and conditions are subject change. And this is true even in a low snow year like 2012. While everyone has been getting very excited about the fact that there isn't much snow up in the Sierra, that doesn't mean that the weather has suddenly turned balmy.
Case in point? Sonora Pass has been closed twice in the last couple of weeks because of snowstorms.
So yes, it's a great year to get up into the mountains. (it's ALWAYS a good year to do that!) But don't assume that since the weather has been milder this spring, that it is going to be much milder every single day from here on out. It can always get snow at high elevations in the Sierra, and from what we've seen, most of the lakes over 9,000 are still at least partially frozen over.
It's still a good idea to plan on lower elevation hikes for early in the summer, unless you are experienced and know how to find your way when the trail is under snow....and the north slopes are slick and icy.
But even lower elevation hikes aren't weather proof. The attached photo is from a trip we took last year, over Memorial Day, and we stayed below 7,000 the whole time.
It still snowed.
And we still had a great time.