Wind speed.

[Hlitner]

As one who has flown many types of small planes, the issue is much less about the speed of the prevailing winds but rather the "crosswind component."  Pilots have computers that calculate the crosswind component based on the wind speed and direction when compared to the runway direction.  Each aircraft (from the smallest single engine to the largest commercial) has a specific maximum crosswind component which is listed in it's manual (they often will have tables).  So while a given aircraft might be able to easily land into a 40knot wind which is coming right down the runway heading, if you change the direction of that wind by 20 degrees off the runway heading it might not be possible to land.

 

Part of the planning when building airport runways is ideally to build them with a heading that parallels the prevailing winds.  But there are times when geographical and other limitations force runways to in a bad direction (to the prevailing winds) which can cause problems for that particular airport.  This is especially true for airports with only a single runway.  In my part of the country we have airports like PHL (Philadelphia) and MDT (Harrisburg) with single runways that can be a real challenge on a windy day.

 

Hank