When Portland, OR, comes up in a conversation with non-locals, the topic frequently turns to how much it rains there. As a Portlander, this is a bit frustrating because people inherently understand weather better than climate, and what most don’t realize is that it actually rains less in Portland than in most cities on the East Coast. Here, by less I mean fewer inches of rain. The tradeoff is that it rains more frequently in Portland (more days per year). But on a per rainy day basis, Portland gets much less precipitation.

The violin plots/heat maps in this post highlight this trend. In Portland (and Seattle), the average precipitation per rainy day is less than a quarter of an inch, and it is extremely rare to have a day with more than one inch. Over the last 50 years, 1.1% of all days in Portland have had more than an inch of rain, but 2.9% of days in New York and 5.0% of days in Miami exceeded that amount. Miami and Jacksonville get an average of about 0.46 in of precipitation per rainy day – almost twice as much as Portland.

And while it does rain more days per year in Portland and Seattle (about 154 days per year), the annual rainfall (36.7 in and 37.8 in, respectively) is considerably less than on the East Coast. The East Coast cities in this analysis all get more rain per year, from 41.4 in (DC) to 61.4 in (Miami). Miami also has a high number of rainy days (134).

So if you hate a little drizzle, sure, stay out of Portland.  But if you need to live on a coast and really hate the rain, you’re better off on the West Coast (specifically, CA).  And the next time you are talking about Portland, maybe toss out the fact that it rains almost 20% more inches in New York each year, and in Portland, you don’t have to shovel snow!

Data source: http://www.ncdc.noaa.gov/cdo-web/

Posted on 18 October, 2013

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