Alaska Cruise by Month: Weather, Whales and What to Wear

Quick answer: Dress in layers with a waterproof jacket in every month. At Ketchikan, Juneau, Skagway and Glacier Bay, July highs are 63–65 °F and lows 47–53 °F; May and September are cooler (Glacier Bay’s May nights average 35 °F), and September brings rain on 17 to 22 days. Most lines also have one or two dressy nights.

How to use it

Pick the month you sail, your cruise line and the number of nights, and tick the ports and glaciers on your itinerary (Ketchikan, Juneau, Skagway and Glacier Bay are ticked for you). The answer gives the range of normal highs and lows across those ports and how many days of the month see rain; below it, each port’s numbers (switch to °C and millimetres if you like), the whales you can expect that month at those ports, where to watch salmon there and whether the night is dark enough for the northern lights, Princess Cruises’ packing list for that month and the National Park Service’s clothing advice for Glacier Bay, then your line’s dressy nights for that length in its own words.

The weather at each port, by month

These are NOAA’s 1991–2020 U.S. Climate Normals: the average daily high and low, in °F, at the weather station nearest each port that also counts rain days (Juneau’s and Glacier Bay’s are their airports, at Juneau and at Gustavus at the mouth of the bay; Icy Strait Point’s is Hoonah). Summer here is cool: no port’s average high reaches 66 °F in any month, and Glacier Bay’s nights are the coldest.

Rain is the other half. The Park Service puts it plainly for Glacier Bay: “Rain is the norm in southeast Alaska.” The table counts the days in each month with at least 0.01 inch; Skagway and Haines, at the top of the Inside Passage, are the driest; May has the fewest rain days at most ports, and every port has the most in September. The Park Service: “April, May and June are usually the driest months of the year. September and October tend to be the wettest.”

The best time for an Alaska cruise

It depends on what you want most, and the normals at the ports answer each wish differently. At Ketchikan, Juneau, Skagway and Glacier Bay, July is the warmest month (an average high of 64 °F), May the driest (rain on 14 days of 31 on average) and June has the longest days (18 h 37 min of daylight at Skagway on the 15th). September is the coolest and wettest: rain on 20 days of 30, and 12 h 52 min of daylight. The Park Service says the same of Glacier Bay: “April, May and June are usually the driest months of the year. September and October tend to be the wettest.” In the tool, tick your own ports and choose warmest, driest or longest days; the months are ranked for that choice.

Whales on an Alaska cruise

Humpbacks and orcas are there in every cruise month; gray whales only at the start. The Alaska Department of Fish and Game says humpbacks “may be seen at any time of year in Alaska, but most animals winter in temperate or tropical waters near Mexico, Hawaii, and in the western Pacific near Japan”, and that in the spring they “migrate back to Alaska where food is abundant and tend to concentrate in several areas including Southeast Alaska, Prince William Sound”. At Kenai Fjords, outside Seward, the Park Service says they “spend from mid-April until November feeding”. Orcas “are found throughout the marine waters of Alaska”, and three kinds “roam the waters around Kenai Fjords National Park”. Gray whales are passing through: the eastern Pacific stock “begins migrating north from late February to May, staying close to the coast from California to Alaska”, then spends the summer in the Bering and Chukchi seas, so May is the cruise month for them. No source counts whales by month, so the tool says only which whales are there.

Salmon runs at the cruise ports

The creeks at the docks fill in July and August. The Alaska Department of Fish and Game’s viewing pages say Ketchikan Creek “fills with spawning salmon each July and August” and that “The planks of Ketchikan’s famous Creek Street are a good spot to watch salmon swim upstream.” At Skagway, “Chinook (king) and pink salmon spawn in Pullen Creek and Pond in July and August.”, beside the Broadway Dock. Juneau’s season is the longest: “From late June through October watch salmon in the fish ladder at the Macaulay Salmon Hatchery.”, and at the Mendenhall Glacier bears “are drawn to Steep Creek when the salmon are spawning from July through September”. A May cruise is too early everywhere but Whittier, where “King salmon run from May through early July.” The department lists no salmon-viewing place for Glacier Bay or Icy Strait Point.

Which salmon: by the department’s species pages, kings run “in the period from May through July”, most sockeye “return to spawn in June and July”, pinks “between late June and mid-October” and coho “enter spawning streams from July to November”; “chum salmon usually spawn in the fall”. It gives no count and no best week, and neither does this page.

Northern lights on an Alaska cruise

For most of the cruise season the nights are too bright. The University of Alaska Fairbanks Geophysical Institute says: “Sunlight prevents viewing the aurora during the summer at high latitudes.” “The skies at night are simply too bright as the sun climbs in the sky until the June 21 solstice and then descends.” It adds that “If active, aurora can generally be seen after civil twilight.” and gives its own season at Fairbanks: “Here in Fairbanks, at about latitude 64.8, our aurora viewing “season” is roughly August 21 to April 21.” The ports are farther south than Fairbanks, so their nights darken a little sooner. This table is the full darkness (the sun more than 18° below the horizon) on the night of the 15th at each port:

From May to July no port here gets fully dark. In mid-August only the southern ports do: Ketchikan 3 h 15 min, Sitka 2 h 5 min, Icy Strait Point 0 h 45 min. By mid-September every port has full darkness, from 5 h 55 min at Whittier to 6 h 55 min at Ketchikan. Darkness is only the first condition: the institute says “To see the aurora you need a mostly clear and dark sky.” and “Although aurora occurs throughout the night, the best time to watch for the aurora is the three or four hours centered around midnight.” For tonight’s activity, see the Northern Lights Forecast.

What to pack

The Park Service’s list for Glacier Bay holds for the whole trip: “Suggested clothing includes waterproof boots, rain gear, a hat, gloves, wool or pile layers or a warm coat.” It adds that “the risk of hypothermia is present at any time of year”. Princess Cruises’ month-by-month list starts in May with “moisture-wicking base layers, cozy fleece sweaters, and a waterproof jacket”, waterproof boots, a beanie, light gloves and a waterproof daypack; adds polarized sunglasses and a sleep mask in June, for the long days; shorts and a light rain jacket in July; waterproof jackets, pants and bags, sweaters and a rainproof hat in August; and a heavier jacket, wool sweaters, warm gloves and binoculars in September.

Dinner on board

Alaska does not change a line’s dress code. Princess has 1 to 2 Dress to Impress nights on a 7-night cruise, Holland America 2 Dressy nights on 7 days, Royal Caribbean 2 Dress Your Best nights on 7 nights, and Norwegian none: the tool reads each line’s own page, through the Cruise Dress Code checker. Pack one dressy outfit for each of those nights; the other evenings are smart casual on most lines.

Worked examples

July, Ketchikan, Juneau, Skagway and Glacier Bay, Princess, 7 nights. Highs of 63–65 °F, lows of 47–53 °F, rain on 11 to 19 days of 31; 1 to 2 Dress to Impress nights.

May, the same ports. Highs of 57–58 °F and lows down to 35 °F at Glacier Bay; rain on 9 (Skagway) to 16 days.

June, all nine ports. Highs of 58–64 °F, lows of 42–49 °F, rain on 10 (Haines) to 17 days of 30.

September, all nine ports. Highs of 54–59 °F and rain on 17 to 22 days; Sitka gets 11.7 inches in the month.

Common mistakes

• Packing for a summer holiday. Even July’s normal highs stay between 60 and 65 °F at every port.
• Counting on an umbrella. Princess’s list and the Park Service both name rain gear and a waterproof jacket.
• Leaving the gloves and hat at home in July. Princess packs them from May, and the Park Service lists them for Glacier Bay.
• Forgetting the dressy nights. Most lines keep them on Alaska sailings.
• Expecting salmon in the creeks in May or June. Ketchikan Creek and Skagway’s Pullen Creek fill in July and August.
• Booking a June or July cruise for the northern lights. No port here gets fully dark before mid-August.

Plan the rest of the trip

Read our Alaska cruise guide, the Alaska cruise packing list, the best places to visit in Alaska and things to do in Valdez. For the rest of the bag, the Packing List Generator builds a list for your days; the Cruise Cost Calculator adds up the trip; and Do I Need a Passport? answers it for a round trip from Seattle that stops in Canada.