I hit the wall

No, not the wall you're thinking. This one was not as painful, but abrupt just the same.
I was out on a 4 hr mtb ride Sunday morning, which started out uneventful. I was met with 70 degree temps with fog and clouds. The fog was thick enough to get you wet, but other than that was just an annoyance.
Hit all the canals and levees down to Mission Trails so as not to have any run ins with un-suspecting cars. Rode around Mission for about an hour, then was headed for Sullivan City for some more trails. That's when I hit the previously mentioned wall.
I was cruising along quite content, no wind, legs felt strong, ipod in tow, just enjoying this fine Sunday morning. Just as I hit Military road, the sky turned darker, wind kicked up, and temps dropped about 20 degrees all in about 100yds.( really, no shit) I was not expecting this cold front to move in until about noon, which would have put me passed the end of my ride, so now I was wet from the fog and sweat, hung out with no warm clothing or gloves.
I was a bit over 2hrs in at this point, so I decided to just ride on to keep the body temp up. The cross winds were brutal......and cold out of the north. Reached Sullivan trails at about 3 hrs, rode about 45 minutes out there, then hopped in with Ed and Dirk for a ride back to la casa (which was the plan anyhow). It was definitely a weird ride.