When I was learning to ride, I was told that the wind chill when you are riding was around -7 degrees per 100km/hr. On cold days, I've found it to be feel much colder than the ambient temp due to wind chill, but on hot days it feels pretty much the same. So I went looking for an explanation for this discrepancy. I found a BOM page that explains this http://www.bom.gov.au/info/thermal_stress/ There's a graph that shows that wind chill factor amount increases as the ambient temp drops and decreases as the ambient temp increases. So what is actually happening is that the hotter it gets, the less chill effect you feel from wind. Conversely the colder it gets the more wind chill you will feel from the same speed wind.