It's possible that one of the sensors froze shut and was frozen shut when you started it up. If that happens, when your Explorer SRS computer goes through it's start-up diagnostics routine, it will throw the code. If your SRS computer sets a code, it takes 256 code free restarts before it will turn the light off. The alternative is that Ford can clear it with their NGS Star tester. You can't clear it with a generic OBD-II scanner unfortunately. If it has since warmed up, you can try turning your ignition on and off 256 times to see if the light stays off. If it does, then the problem has corrected itself (probably by thawing out). That was how I ended up clearing my flashing air-bag light after I started my Explorer with the air-bag fuse removed. I un-plugged the connector to my fuel shut-off switch after the first 15 or 20 cycles though since I got tired of listening to my fuel pump energize each time. It took about an hour to do and was cheaper than going to Ford. I had the advantage of knowing there was nothing wrong with my air-bags though once I put the fuse back in. Disconnecting the battery won't help either since the SRS has it's own internal backup power source. If it doesn't clear with the on/off sequence then there is still a problem that will likely result in a trip to Ford.