We have been in June and August --- the weather is much the same all summer (the temps are influenced by the water temps), but June isn't as rainy as Aug. Out on the decks while cruising or going through the fijords is COLD. Plan on coats, hats, and gloves; you can always take them off. We love the Alaska cruises; the scenery is breathtaking!!! Packing for a cruise is challenging. Daytime is very casual, jeans & tee shirts; you won't spend much time in or around the pool, unless your ship has a covered pool, but you may want to hit the jacuzis so pack swimsuits - - just make sure you take a warm robe to wrap up in when you getout :) (check to see if robes are provided). In the evening you need to dress up a little for the dining rooms, they call it 'resort casual', think "business casual". An then there are the formal nights when you get quite dressed up -- suits/blazers and dresses/gowns (tuxes aren't necessary, but some men do wear them). Check with the airline for luggage restrictions, weight and charges so you don't have any surprises at the airport. Make sure you go to the cruise ship website to read thier suggestions, there should be average temp info for the cities you will visiting also. You should also fill out all the " paperwork" on-line so that check-in at the dock goes quickly and smoothly. If you are going in/out of Canada I think you need a passport. It also helps to sign up for the shore excursions on-line ASAP, many of the popular tours/events will sell out quickly. Many of the shore excursions are more expensive than in the Caribbean, but they are worth it. We signed up twice for helicoptor tour of the Hubbard Glacier, and had it cancelled both times due to rainy weather that grounded all flights. Oh well. Have a back-up plan. One more "caution" -- it seems like every time you turn round someone is taking your picture; and you will want to buy every single one !!! Be selective or you will pay a fortune (we do plan on getting our pictures taken on formal night and buying several). I won't say don't overeat, because that's half the fun. We just make sure we go for several walks around the promenade deck and take the stairs rather than the elevators. We love cruising; hope you have a wonderful time.