The sound of rushing wind can seriously disrupt communications from mobile or portable stations.
Often the affected stations don't realize they are transmitting wind noise through their microphones.
Net controls may not recognize the sound of wind noise -- telling stations to improve their position when the signal is actually fine.
On windy days, it's best to face the wind and, if possible, cup your hand behind the microphone. Alternately, seek cover or sit inside a vehicle to cut down on the noise.
Of course, keep your vehicle windows closed while talking and driving.