I live in Southern California, and we experience a phenomenon known as "Santa Ana Winds." These winds can literally reach hurricane speeds, I heard that a gust reached 108 m.p.h. today. These winds are invariably extremely dry and typically result in a rash of wildfires. Such has been the case today.
I was driving back to my house from Lakewood, an easterly trip down the 91 freeway. Santa Ana Winds originate in the Great Basin and thus are typically northeasterly. As I tooled down the freeway at my usual 55 m.p.h., I noted sand, pebbles, leaves, etc. blowing into my windshield as my car experienced significant buffeting. Looking at my miles per gallon display, on a level stretch where I expect to see 21.5 m.p.g. I noted 17.2 m.p.g. I had heard that the sustained winds in this area were on the order of 30 to 40 m.p.h. with possibly something like a 22 to 29 m.p.h. headwind component (it was off my nose by maybe 45 degrees), and so presumably that's the sort of gas mileage I could expect in the range of 80 m.p.h. (using the average of 22 and 29 as the headwind component).
Needless to say, I wasn't pleased but I wasn't willing to slow down to, oh, say, 30 m.p.h. to attempt to save fuel. Even my compulsiveness has limits. Besides, I didn't want a crash or a ticket. I've been pulled over for driving 55 m.p.h. in the right lane. Though the officer wouldn't say why he pulled me over, I'm sure he thought I'd been drinking (I've been sober for 28 years) and that I was trying to avoid being pulled over. He didn't even ask for my license and registration, he just shined his light in my eyes, told me to drive carefully, and left.
So what's to be learned from this headwind experience? There's not much to be done about it, but I can at least plug the numbers into my fuel consumption versus speed equation and see if they fit. Maybe my mileage gauge can serve double duty as an anemometer.