Climate & Seasons
There is one special rule that has been found to work for most travelers in Alaska, and that is to always be prepared for one season COLDER than the time you are travelling. This is especially important for those who travel early and late in the season. Likewise, if your plans are going to take you into any of Alaska's many mountainous regions, be prepared for cooler temperatures and higher winds.
June, July & August -- Summer in Alaska is a miraculous time, when the sun refuses to set, the salmon run upriver, and people are energized by limitless daylight. The sun dips below the horizon in Anchorage for only about 4 hours on June 21, the longest day of the year, and the sky is light all night. The state fills with people coming to visit and to work in the seasonal fishing, timber, and construction industries. Weather gets warmer, although how warm depends on where you go. June is the driest of the summer months, July the warmest, and August generally the rainiest month of the brief summer, but warmer than June. In most respects, June is the best summer month to make a visit, but it does have some drawbacks to consider: In the Arctic, snow can linger until mid-June; in Southcentral Alaska, trails at high elevations or in the shade may be too muddy or snowy; and not all activities or facilities at Denali National Park open until late June. It's also the worst time for mosquitoes.
May & September -- More and more visitors are coming to Alaska during these "shoulder months" to take advantage of the lower prices, reduced crowds, and special beauty.
May is the drier of the 2 months and can be as warm as summer if you're lucky, but as you travel farther north and earlier in the month, your chances of finding cold, mud, and even snow increase. In Alaska, there is no spring -- the melt of snow and resultant seas of mud are called breakup. Flowers show up with the start of summer. Many outdoor activities aren't possible during breakup, which can extend well into May. Except in cruise-ship towns, most tourist-oriented activities and facilities are still closed before May 15, and a few don't open until Memorial Day or June 1. Where visitor facilities are open, they often have significantly lower prices. Also, the first visitors of the year usually receive an especially warm welcome. The very earliest salmon runs start in May, but for a fishing-oriented trip, it's better to come later in the summer. Cruise ships begin calling May 1, and the towns they visit swing into action when they arrive.
October, November, April -- I always love Alaska, but I love it least during these transition months between winter and summer. From Southcentral Alaska northward, snow and ice arrive sometime in October; in Southeast Alaska, it is the month of cold, unending rain. Winter starts in November, but you can't count on being able to do winter sports and darkness is prevalent as the year's shortest day approaches. April is a month of waiting, as winter sports come to an end and summer activities are blocked by melt and mud (although spring skiing can still be great in high-snow years). In-town activities are down in these months, too; with few visitors, many facilities are closed.
December through March -- Winter is the whole point of Alaska. For sightseeing, the scenery is at its best (although there are far fewer wildlife-viewing opportunities). This is the time to see the aurora borealis. Communities get busy with activities such as sled dog and snowmobile races, theater, music and other performing arts, ice carving competitions and winter carnivals, and all the rest of the real local culture that takes a break in the summer, when most visitors come. If you enjoy winter and its outdoor activities, an Alaska visit is paradise, with superb downhill, cross-country, and backcountry skiing; snowshoeing; snowmobiling; dog mushing; ice skating -- anything that can be done on snow and ice.
By far the best time to come is late winter, February and March, when the sun is up longer and winter activities hit their peak. Anchorage's Fur Rendezvous is in late February; the Iditarod Sled Dog Race is in early March. Visiting in late March could mean thin snow at lower elevations for cross-country skiing, but downhill skiing and skiing at backcountry locations keep going strong. At Alyeska Resort, south of Anchorage, some skiing goes on through Memorial Day. In Homer, you can cross-country ski and go salmon fishing on the same day in March.
If you come in winter, you sacrifice some popular Alaska experiences. Some tourism-oriented towns such as Skagway close down almost completely. In places on the ocean, most activities and attractions are closed for the season, but services remain open for business travelers. Inland, where winter sports are better, there is more to do. Hotel prices are often less than half of what you'd pay in the high season. Quite luxurious rooms sometimes go for the cost of a budget motel.
What to Wear
You'll find little use for a tie or any formal attire anywhere in Alaska, but you do need to prepare for broad swings in weather.
Summer -- You're not going to the North Pole, and you don't need a down parka or winter boots weighing down your luggage. But you do need to be ready for a variety of weather, from sunny 80°F (27°C) days to windy, rainy 50°F (10°C) outings on the water. The way Alaskans prepare for such a range is with layers. The content of the layers depends on what you'll be doing, but everyone should bring at least this: warm-weather clothes, heavy long-sleeved shirts and pants, a wool sweater or fleece equivalent, a jacket, and a waterproof raincoat and rain pants. Gloves and wool hats are a good idea, too, especially for boating trips. If you'll be camping, add synthetic thermal long underwear and wool socks, and make your jacket thick synthetic fleece. Combining these items, you'll be ready for any summer conditions. For hiking, bring sturdy shoes or cross trainers.