The sun will rise and set, BUT it will still be light through the night! Make sure to get sleeping accommodations with black out curtains.
Alaskan weather is bipolar, but the average temp in July is in the 70's.
We always recommend that guests pack summer outfits with a few pairs of pants/jackets/hoodies. Don't underestimate a hot day in Alaska though. It can get hot, and most places/buildings do not have air conditioning.