It's a well known fact that due to air resistance increase of speed on a bike takes non linear increase of power, so the huge marginal increase of power needed to go faster while riding at around 40-45km/h has made average top speeds of the peloton stay in this range for many years. I was wondering if the air drag plays such a major role why doesn't wind affect the average speeds more? 

I'd imagine that given at these speeds air resistance is a major factor (it's almost like a wall if you look at the power curve) the cyclist relative 'airspeed' in the wind should also be a major factor but it doesn't look so judging from the single day race results like Milan-San Remo (which has constant almost straight route so should be strongly affected by the wind). You can see results here: <http://www.bikeraceinfo.com/classics/Milan-San%20Remo/milan-san-remo-index.html>. If I were to guess I'd expect that wind should make the differences on range of at least -/+10 km/h but clearly this is not the case (it's more like a 37-45km/h range). Why is that so? 

(There was an incredibly interesting question here about the increase (or lack thereof) of avg speed of TdF winners over the years: [Why aren't Tour de France riders going any faster?](https://bicycles.stackexchange.com/questions/7661/why-arent-tour-de-france-riders-going-any-faster) I understand that in multiday event the wind effects and tactics will cancel out but what about single stage races?)