For me is about .25 miles this morning. This week is another (w4+r6)2+w5 week. The humidity was as bad as some of summer's worst today and breathing was not easy. As a result, the second run segment ended up being a w4+r4+w2+w5. Also, as a result, I was about a quarter mile shorter of what I normally do in that time.
I won't sweat it too much as tomorrow's the first time I move from a walking chunk with a little touch of running to a chunk of running. We'll see how it goes.
Hopefully the humidity breaks tonight and we're back in the right season again. It may take a few days to get there... we'll see. In the meantime, if you think that minute or two doesn't make a difference, think again.