I've given up using wind direction to determine my route. I've had plenty of rides where the wind changed 180 degrees within a few miles, so I just stopped worrying about it.
About the only thing I pay attention to now is the wind forecast. (Yes, the forecast.) Here's the secret: take the forecast wind speed, double it, and you'll be in the ballpark.
The forecast wind direction is another matter. It's really just a random number between 0 and 359, but it's useful if you're having trouble deciding what jersey to wear and you don't have a coin to flip (0-179, choose red; 180-359, choose yellow).