This is based on what my guests have worn that seems most popular or most needed during their time here. I'm very warm-blooded and will be toddling around bare-footed and in light summerwear until the snow flies. Most of you will likely be chilly at some point during your summer vacation to Alaska.
Our summer daytime highs average about 72 with nighttime temps falling to between 55-62 approximately. In my location, in the Matanuska Valley, I'm ringed on 3 sides by mountains, with temperate ocean influences from the water near Anchorage. At the B&B, typically it is about 4-6 degrees warmer than Anchorage in the summer and 4-6 degrees colder in the winter, but nothing like the high-highs and low-lows felt in the Interior near Fairbanks. Check the current weather here.
It's very typical for a day to go like this: At breakfast, it could be cloudy or overcast or even drizzling. Guests will bemoan that this might be a rainy day. I heavily encourage guests to hit the museums or shopping right after breakfast, to have something to do indoors while it's still somewhat chilly or wet. The cold or wet may linger towards lunchtime, but be warming slightly. This is a good time to be driving towards your main activity of the day and/or getting a bite to eat. All of a sudden between 1-3 p.m., gloriousness bursts out and it becomes a stunningly gorgeous day with blue skies, a few high, wispy clouds, and warm or hot sun. You'll want to go and go and go and do as much as you can in such beautiful weather. This is not the time of day to ponder what to pack for a hike or be in a store--be ready and GO. The late afternoons turn to achingly splendid examples of what summer in Alaska can be like. Warm breezes, brilliant colors, sun glinting off of water...It'll feel like you never want the moment to stop. This type of weather will continue until about 7:30 or 8 pm and you'll lose track that it's no longer 4:30 in the afternoon because the sun will have hardly moved from its zenith. You may realize that you're starving and go to dinner. It could be 15 degrees cooler an hour later at 9-10 p.m. as the day wanes. For this day, you'll likely want a warmer jacket but be able to shed it down to "summer clothes" during the warmest part of the day.
For the prime summer months, you'll likely enjoy having short-sleeved shirts with a longer-sleeved shirt or light jacket for times when you're in warm sun. In case a breeze comes up, a cozier fleece for rainy or cool days is good. It's up to you whether to bring shorts. If you wouldn't wear shorts at 72 degrees, you probably can do without them here. Most folks are comfortable in a light twill type of pant, or those outdoors pants that have legs that zip off are handy, too. Jeans are not very practical. They tend to be too hot during the warmest part of the day, and too heavy of a material to dry easily if you get wet accidentally such as when crossing a small stream.
For shoes, good ol' tennies will probably get you around most places. Anything dainty is a bad idea. Walking here involves dirt and dust and possibly brushy plants like grasses. Strappy sandles beg for a turned ankle or sand in your shoe or chilly toes. Don't feel like you need to lug a pair of heavy hiking boots up here if you don't intend to hike more than an hour several days of your trip. Most of the trails are not extremely rugged unless they're ones where you're committing to summit a mountain over a period of a full day or days. I can't tell you how many guests pull out a box of brand new fancy hiking boots, wear them on a walk where they weren't needed, and come home with painful blisters. A simple tie shoe such as an athletic shoe or a leather pair with socks will be the most comfortable and practical so you can go where you want to go in towns and on light adventures such as glacier treks.
Be sure to layer and take a warmer layer with you when you go out for the day. Bulky, heavy-duty raingear won't be needed unless you plan to stay outside in the rain regardless, such as for day-long hikes. For most tourists, a windbreaker or fleece jacket will keep the rain off long enough to get you from the car to your next activity or destination. Most of our rain tends to be drizzly, spotty mists, not penetrating, soaking downpours. Here's a chart of what to bring for which seasons.
You may think of Alaska as a land of extreme cold and danger, whether summer or winter. It's true that hypothermia can happen in summer, but usually that has to do with falling into frigid water, getting lost in the rain, when someone panics or otherwise fails to use common sense. Additional clothing precautions are needed if you are going unsupported into the backcountry or will be undergoing a long recreational hike or other adventures which will last more than a few hours.
I am a big proponent of under-packing for a vacation to Southcentral Alaska. You don't need every single possible thing. You need a couple of comfortable blouses or t-shirts, pants and possibly a pair of shorts, a light jacket and warmer fleece, and practical shoes. Nothing you'd go to in my area or in Anchorage will require "dressy" clothes. You can go to the best restaurants in Anchorage in Docker pants and a shirt--this is all quite normal in a place where tourists outnumber locals 3 to 1 and where Alaska Formal means you should wear shoes.
Packing light can free you up to have time to see as much of our great state as possible and not worry about managing suitcases full of stuff. There are laundromats everywhere, so it's easy to give everything a wash every few days. We can do your laundry for you, too, at Alaska Garden Gate B&B, while you're out for the day.