FAQs about the Natural History of the Inside Passage

1. What's the average rainfall in Southeast Alaska and what towns have the heaviest rainfall?

Southeast Alaska's maritime climate is characterized by relatively mild, cloudy, wet weather. Along the Inside Passage from Juneau to Ketchikan about 50 percent of the days have measurable rainfall (>=0.01 inches) during the cruising season, mid-May to mid-September. However, the rain is seldom heavy enough to cancel your cruising plans.

There's no hiding the fact that Southeast is damp. Ketchikan on average gets 137 inches of precipitation a year, Petersburg 110 inches, Sitka 86 inches, Wrangell 79 inches, Glacier Bay 70 inches, Juneau 58 inches, and Skagway, which is in Glacier Bay's rain shadow, averages only 26 inches. (Average annual precipitation figures are from the Alaska Climate Research Center and based on data from 1971 to 2000.)

Climatology data should be considered with a critical eye and all weather elements available should be taken into account. For example, let's say you are going to visit Sitka and Ketchikan in July. You will find that on average Sitka has 18 days with precipitation while Ketchikan only has 15. You may then think that Sitka is slightly wetter than Ketchikan for this period. However, if you also consider the average amount of precipitation you will see that Sitka has 3.85 inches of rain and Ketchikan 6.43 inches. Hence Ketchikan receives almost twice as much rainfall in an average July than Sitka. Cruisers may find it useful to compare the climatology data of their destinations with the data for their hometown to provide a base of reference.