Wednesday, December 10, 2008

A Sudden Chill

At the end of the calendar year, San Francisco seems to get cold out of nowhere and all of a sudden. Like, really cold... and really suddenly. It's strange: last week I was cycling in shorts and a t-shirt, and this week I'm urgently ordering a cord of wood for heating fuel during the winter. A couple of days ago I wore three layers out in the evening for the first time in months. Wendy brought handwarmers and wished for a scarf.

What's going on?

Turns out Wendy and I were brought up in symmetric climates, where the temperature varies in evenly spaced peaks and troughs. By way of illustration: here, courtesy of, are the monthly high and low temperatures in Denver, where Wendy spent her youth:

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and here are monthly highs and lows in Sheffield, where I grew up:
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You can see the similarities. Sure, Denver is more extreme on the high side as well as the low side, but the two exhibit basically the same pattern: it heats up for six months, it cools down for six months. Notice how this means that the warmest and the coldest months are a good while apart.

Then there's San Francisco.

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It starts cold in January and gets warmer and warmer and warmer until about October and then boom---the temperature plummets. The second-warmest month is October and the second-coldest month is December!

Of course, it's all relative. But it's nice to know that there's at least some scientific basis to the perception that winter comes out of nowhere in San Francisco. Brrr.

In other news, the printer is back today and on top form. I'm going hardcopy crazy.


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