Originally Posted by rm -rf

It depends on your speed, the wind speed, and wind angle. A pure 90 degree side wind looks like 45 degrees from the front if the wind is 20 mph and the bike is 20 mph.

This HED yaw calculator is fun to play with. (Scroll down to the Apparent Wind Calculator link.)

You know, of course, that riders speed up until a tailwind becomes a headwind.