Today I ventured out for my very first "very cold barefoot run". It's been a bit late coming as last week saw large parts of the UK covered in snow, and if your area wasn't covered in snow, it was freeeeeeeezing. My area was a bit of both - we had a light dusting of snow on two days and then sub-zero temperatures for the rest of the week.
I've been doing a fair bit of reading on cold weather barefoot running and I've drawn a line in the sand (or should that be snow) as to when I will and will not head out for a run barefoot. That line is 0°C. This is technically freezing point or water at sea-level and if the air is this cold, there's a very good chance the ground and water on it will be too - probably colder once you add the salt and grit.
On Monday I went out in Vibrams as I had scheduled a fast tempo run along the Thames which would take in quite a long section of pavement that was quite heavily gritted. It was also bordering 0°C so I didn't want to risk it. Today it was definitely warmer, so I decided I'd brave the cold and I'm glad I did. It wasn't anywhere near as bad as I thought it would be.
... and then headed out a little on the sweaty side. Normally I'd strip off at this point but I held back and stayed wrapped up for my entire run. My body and feet soon cooled down a bit in the 1 mile to the field in which I did my 6x600m intervals at 3k pace. The cool down wasn't dramatic and I soon found my feet warmed up again too.
The coldest part of the run was running on grassy sections no one else had passed over that day. The grass was still a little dewy and cold, but thankfully not frozen.
Bar the very strange looks I got from people I passed, my first very cold barefoot run turned out to be a great success and provided the temperature is above 0°C on a given day and I'm not running through heavily gritted areas, I'll continue to do my runs barefoot this winter.