Rain Gauges and the Alaska Rainy Season

Not all of Alaska is in the rainiest time of the year right now, but the southeast arm of the state, also variously known as the panhandle, the Inside Passage, the Banana Belt, or just plain Southeast sure is. In fact, I like the term rain coast. Farther north the rainiest time tends to be earlier in the year. With a few exceptions, the wettest month in Southeast is October, in Southcentral and the Interior it is September or August and along the north coast and most of the Bering Strait and Bering Sea coasts it is consistently August. The southwest coast and Aleutian Islands don’t show as clearly defined wettest month but there is no doubt that September through December or January is the wet time. These graphs illustrate. The green line is the precipitation, the others temperature. Note that the scales are the not the same on all graphs. The precipitation scale (on the right) is the same for all but Ketchikan, where it had to be expanded upward to handle the larger amounts. The temperature scales are less consistent.  (that’s what you get when you borrow your graphs…these borrowed from the Western Regional Climate Center.)

cli302010.pl-KTN cli302010.p-DUTl cli302010.pl-GKN cli302010.pl-BRW

Wherever you are, except maybe Death Valley, you might want to have a rain gauge to keep on top of the details at your location. What other piece of technology is so inexpensive, easy to use, durable and accurate? Here’s my 4 inch plastic model. (click for bigger picture). It consistently reads very close to the official NWS coop 8 inch rain gauge located less than mile away.


The overflow feature is handy here is Southeast. It works just like its big brother, the 8 inch metal gauge, which is the standard at the NWS and around the world. When the gauge begins to collect rain, it is funneled into the inner tube where the amount of rainfall can be read easily read in 1/100’s of an inch on the scale (A). When 1.00 inches have accumulated, the inner tube is full. Don’t worry, there is a channel (B) which directs the overflow into the outer tube which can hold much more. When it’s time to take a measurement, the inner tube is emptied and the overflow poured into, and measured with, the inner tube (filling and emptying as many times as needed) to get the total. In this photo you can see that the rainfall came quite a ways up the overflow tube (C) while our family was away for three weeks. The total was 5.20 inches (132 mm) (and that was in August, not our real rainy season). If one had left for the same dates from Ketchikan, even the overflow tube would not have been able to handle the 16.05 inches (408 mm) that fell there!

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