What's Up With That Pesky Afternoon Wind Shift?

What's Up With That Pesky Afternoon Wind Shift?
SEATTLE - Jim M. wrote in saying he commutes by bicycle from Lake City to Montlake, and noticed he'd have a headwind in the morning as he went south, but then had a headwind again going north in the afternoon.

While that doesn’t seem fair, it actually is -- at least, meteorologically speaking.

In Seattle, fair weather usually brings north winds, while cloudy, rainy weather brings a south wind. With the common summer marine pushes (the "morning cloud, afternoon sun" routine), the push of marine air off the ocean overnight comes in from the southwest, so the morning features a southerly wind.

But as the marine air burns off, we switch to a more northerly wind. So the morning south wind and afternoon north wind is pretty common this time of year. On hot days, it'll be north wind all day, and in the winter and fall/early spring, it'll be a southerly wind most days.