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Started: 2019-01-29 19:49:57

Submitted: 2019-01-29 20:52:01

Visibility: World-readable

In which the intrepid narrator muses on the climate data comparing three randomly-chosen cities

Thanks to the climate data on Wikipedia, I put together a series of handy graphs comparing the amount of rain that Seattle gets versus two other randomly-chosen cities, San Francisco and London. (I considered including Boulder, since I lived there longer than anywhere else, and I understand (and have adapted to) the climate there; but the climate data on Wikipedia was not presented in the same format, and at the time I made the charts, NOAA's detailed climate data was unavailable due to the Trump Shutdown.)

Rain in Fremont
Rain in Fremont

First I present the average monthly precipitation, in inches. We see that London gets consistent rainfall year-round, but both Seattle and San Francisco have a strong annual cycle: rain in the winter, and drier in the summer.

Average monthly precipitation

Overall, year-round, Seattle gets 58% more rain (measured in volume of rainfall) than San Francisco; and Seattle gets exactly as much rain as London. (Somehow, somewhere, I heard that Seattle doesn't get very much rain compared to other cities; but this turns out to not be the case.)

It's also worth considering the number of days of rain each city gets per month. (In the source data, this is specifically measuring the number of days with measurable precipitation, at least 0.1 inch or 1.0 millimeter.)

Average precipitation days

Overall, year-round, Seattle has double the number of rainy days as San Francisco; and Seattle about 40% more rainy days than London.

Finally, let's look at the hours of sunshine each city gets per year. All three of my randomly-selected cities are in the northern hemisphere, so they enjoy the same planetary axial tilt. In every month, Seattle gets more hours of sunshine than London, and San Francisco gets more sunshine than Seattle.

Mean monthly sunshine hours

Overall, year-round, Seattle gets 29% less sunshine than San Francisco; and in December and January Seattle gets 65% less sunshine than San Francisco.