Just Like a British Summer
Last year we flew from Portland Oregon to Anchorage and spent three days there. It was August, and it did rain but we also had some good sunshine. If you're used to our summer weather in the UK you'll find no surprises in the southern Alaskan summer (other then the ever-present snow and ice in many parts!).
We hired a car and took a day trip to Seward. The scenery along Turnagain Arm is fantastic and highly recommended. Worryingly, there are a lot of bullet-hole-ridden road signs! We also took a 2-hour boat trip out of Seward into Resurrection Bay. There was not a cloud in the sky and it was great. On the trip back to Anchorage we paid a visit to Exit Glacier. It was raining by the time we got back to Anchorage, so clear sunny conditions can easily give way to rain.
You'll find many float planes in Anchorage and elsewhere. We didn't use them, but they must be a great way to see areas that are otherwise inaccessible.
We flew into Anchorage in darkness (arriving at about 3am!) but we flew out in daylight, and it was another clear day (I think we got lucky!). As a result I got some great photographs of mountains and glaciers on the way to Seattle. Something you won't get from a boat!
This was a great 'taster' and it got us interested in Alaska. The lack of roads probably means there's more unspoiled scenery in Alaska than anywhere else in the USA. Next time we'll try further southeast - Juneau, Sitka or Ketchikan - and possibly north to Fairbanks.