I would bring layers. I was in AK in early May a couple of years ago. I would bring enough layers that you can shed or add layers as needed. Four or five layers?
But two years ago about May 15th there was still a ton of snow.
If you're referring to spring 2008, we had a ridiculously lousy spring/summer that year. Specifically, that was the year it snowed 2 feet in Anchorage on April 25th, followed by a summer that had a whopping two (2!) days that broke 70 degrees.
April this year was a bit gloomy, but Anchorage is very nice right now; mostly sunny days and highs around 60.