Went to alaska in 1996 at end off august the weather was nice rained once at keticka.
By ship only in the Summer but watch out for the mosquitos which fairly fierce but not malarial. Late Spring can also be attractive. Go inland to see the contrasting scenery.
We are seasoned HAL cruisers and have been to Alaska a few times over the last 18 yrs, all with HAL and all during the school holidays July and August.We've cruised Vancouver to Vancouver, Vancouver to Anchorage and taken a land tour from Anchorage. The weather can be varied, wet/dryish,cool/warm and inland,hot so just take layers and you will be fine late spring through to early autumn although bear in mind our early autumn can mean the start of winter and snow in Anchorage.We must have been lucky as mozzies have not been a problem although as I am the equivalent of xmas dinner to them, I do use a repellent [Boots silver topped 50% deet] when in forests/national parks. HAL has become more 'child friendly' over the years on certain ships/routes during school holidays so that might be a factor to think about.There is just so much to see and we are thinking of our next cruise to Alaska, this time without children so spring or early autumn will be our target months. As in the past HAL will be our cruise line.Have fun.