Just in case it hasn't been said... it's HOT. We went last 23-27, and it was ~95 every day. Luckily, it was at least a little overcast for most of it, so the sun wasn't on our heads, too.
We've found on our last two trips (June '06 and August) that AK doesn't have a lot of places to cool off, so be wary. Also, it will rain, on occasion. We were a little surpised - on our AK day, we were taking a bus back to WL and it started to rain. We'd planned on swimming that night, but the rain actually kept up until bedtime. The rest of the time, the rain lasted maybe a half hour.