How Does Cold Weather Affect Your Race Pace?

The cold weather has actually helped my pace. I struggled all summer long and didn't feel like I was making any progress this year with my running pace, but as soon as the weather started cooling down i have seen a big difference. I actually had a new 5K PR a couple of weeks ago. It was a night run and temp was in the 30's. 

However, I haven't ran in temps as low as that, so I can't say how I would do if it was 1 degree outside. Coldest I have ran in is 20's. This year i have enjoyed running in the cold weather because I feel like I can push myself really hard without overheating and my heart rate stays lower. 

I know that I can estimate a pace 15 seconds slower when I wear tights and cold weather gear.  Another 15 second slower pace when I bring my fuel belt with water.

All that clothing certainly can slow you down. I'm always a bit slower once I need pants instead of shorts. Various thermal layers can slow down too. I love cookies as well, but eating a ton of them can affect me some. And anything that causes breathing issues will slow you down. The muscles might need some more warming up, but should be fine once they get it. The three things highlighted are where to look, so if you can address those then you should do better.

The effects of temperature on running that I have seen put the optimal about 55 degrees with an 8-12 second negative effect on a 5k for every 5 degree rise with that amount increasing as it gets hotter.  Not sure how the scale would go as it gets colder but I would think that it would be slightly less of an impact.

For me, when it gets colder I wear more gear that restricts my movement slightly and the extra weight can be significant, especially as those layers get wet from sweat or the elements.  I have been amazed at how heavy my stuff has gotten after a run.

My experience is the longer the race, the less it affects your time. It was bitterly cold and a very slow start at Marine Corps in 2011, but after around 5 miles I was warmed up and fine. Also did a cold and rainy duathlon and just never got warm, and running off the bike was horrible. Ideal for me is 45-50 for marathon, 60+ for short distances.

My lungs would not handle 1 degree. That's dreadmill weather.

This is totally me. 30 degrees and I'm in a thin long-sleeved shirt that is removed if I'm doing speedwork and get really warm.

That being said, 1 degree is SO extreme that it would definitely affect my pace, especially as I have exercise-induced asthma which is really set off by hard runs in cold temperatures. Coldest I have ever raced in was 10 degrees. 1 degree, I wouldn't do it. Treadmill weather.